Vidya - Agave

If you don't have Vidya - Agave yet but want to try her out, she is available as a Trial Operative in Story Chapter SP3 "Operation Midnight" ( Main Story // Legacy // New Hentiro )

Agave's damage is ok, she has decent mobility, her skill has auto-aim and AoE as well as long-range, so even ignoring Agave's two biggest... *ahem* assets, I think she is one of the best characters for casual play, just because she is so simple-to-play and easy-to-use.
For endgame content, extreme powercreep has meant that Agave doesn't have the dps to be a competitive Main DPS any more, but Agave is the best Parts Breaker in the game by a huge margin, and whilst Parts Breaking isn't overly useful at endgame, when it is needed Agave is the default and best choice, with her support skill being a nice 20% ATK buff as well, which also makes her a decent early-game support due to how little investment is needed to get the buff.

Note that Vidya's other exosuit form (Vidya - Celestial Swan) is the games strongest support by a vast margin.
Don't get confused between Agave and Celestial Swan. Agave is not a good dps support and using her as a support will not result in a large increase to your dps.

The Basics

Role: Agave can fill all team roles
(Some better than others)
(She's best as a Parts Break)
Deals Electric Damage
Weapon Type: Pistol
Deals almost entirely skill damage
Mobility is good

How to use Vidya - Agave as a Parts Break

If Parts Breaking isn't needed:
Keep Agave off-field, spamming her Support Skill off-cooldown

When Parts Breaking is Needed:

Swap Agave in
Parts Break with her by spamming her DPS rotation below
When done, immediately swap Agave out and your main dps back in

(Note Agave's Support Buff affects the entire team, including herself if she is switched back in whilst it is active, so if you time it well she can use her Support Skill to buff herself too.)

How to use Vidya - Agave as a DPS

1. Use her standard skill until you run out of S-Energy
2. Use her Ultimate
3. Shoot enemies until all her S-Energy has been recovered

Repeat

How to build Vidya - Agave

Weapon: Snapshot Ace / Pure Verdure
Weapon Parts: Max ATK
Logistics Squad: Chaya
Basic: +10.0% ATK
+106 Alignment Index
Special: +8.5% Electric Damage
Best supports to support Agave:
Vidya - Celestial Swan
Siris - Freefin
Marian - Aquila
Enya - Exuvia

Specifics:

Standard Skill and Standard Attack

Standard Skill

Agave fires a homing projectile at the target, which deals PBAoE Electric Damage on hit.
Using the skill continuously increases its "Phase" - projectiles fired at higher Phases do more damage with larger AoE, but use more S-Energy.
The damage increase from phase increases is massive - Phase 4 deals around 3.5x the damage of Phase 1.
If Agave shoots her gun or doesn't use the skill for 2 seconds, Phase resets back to 0.

For each hit with her Standard Skill, Agave gains "Personal Flair" (which is used for her Ultimate).
This is the number above her S-Energy gauge in the bottom-left of the UI.
Each hit gives Agave 1 Personal Flair per Phase level.

If her standard skill hits a destructible part, it also damages another destructible part. (Or deals more damage if only 1 part is available to hit)
Hitting a destructible part also reduces the next skills S-Energy cost by 25% per part hit.
If a destructible part is destroyed, then Agave gets 50% reduced S-Energy consumption for 3s.

If the skill defeats a target, her next skill usage with 5 seconds doesn't use S-Energy.

Agave can move whilst using this skill, but it isn't quite as fast as moving normally, meaning she has lower mobility than just running about normally, but her overall mobility is still decent as she can still move freely whilst using her Standard Skill, and at decent speed.

Standard Attack

Agave shoots her gun.
Agave recovers S-Energy per hit with her gun.
Since Agave does not naturally recover S-Energy whilst she's on the field and in combat, landing hits with her gun is her only in-combat method of recovering S-Energy.
She does recover S-Energy when not in combat though, so for casual gameplay she can clear a group using her skills and then just run to the next group, and her S-Energy will almost always have fully regenerated by the time she gets to the next group.
This means that for casual content, you may never need to actually use Agave's gun except for the missions final boss.

Note that the Skill Damage buff from her 4* and 5* signature weapons are removed whenever Agave shoots.

Ultimate Skill

Agave deals AoE damage in front of her - the more Personal Flair stacks she has, the more damage dealt.

Note that the damage of Agave's ult isn't quite linearly proportional to the number of Personal Flair stacks she has.
Agave's standard skill rotation tends to end up giving her around 30 Personal Flair, but this can vary depending on certain things (notably M1).
Using three ults at 30 Personal Flair deals 20.5% more total damage than one ult at 90 Personal Flair.

Agave loses her Skill DMG buffs when she shoots, so make sure to always use her ult after using her Standard Skill - never use her ult directly after firing her gun.
Her 4* weapon needs 4 standard skill casts to max its buff. Her 5* weapon needs 3 casts.

If Agave has 20 stacks of Personal Flair or more (which she should always have if you're doing her rotation properly), then after using her ult her next Standard Skill usage within 10 seconds skips straight to Phase 4.
As such, she should use her standard skill until she runs out of S-Energy, and then ult immediately.
This allows her to keep her Skill DMG buffs from her gun and have them apply to her ult, whilst also skipping to Phase.4 after regaining her S-Energy, which allows her to not waste S-Energy using weaker Phase 1/2/3 casts.

Whilst you can use her standard skill, shoot, repeat until her Personal Flair stacks are at max, and then Ultimate, this results in less damage than just ult-ing immediately after her S-Energy runs out.
Her ult has some base damage, so the more casts Agave does the more total damage she inflicts.
E.g. Two ults at 50 Personal Flair deal more total damage than one ult at 100 Personal Flair.
Not using her ult would mean that after shooting she would have to start her standard skill from Phase.1 again, wasting damage by not making use of the buff that allows her to skip to Phase.4, and again - Phase.4 deals a lot more damage than Phase.1 does.
As such, getting to 100 Personal Flair is just a DPS loss, so avoid doing it and instead just Ult when she runs out of S-Energy as per the 3-step rotation listed in the "How to use Vidya - Agave as a DPS" section above.

Support Skill

Agave's Support Skill causes her to deal Electrical DMG + Paraylze (for 2s) in an AoE in front of her.
Note that the stun and damage from her Support Skill are not really very useful - you're using it for the ATK buff [below] only, really.
This uses 20% of Agave's S-Energy. If this causes Agave to use more than 10 S-Energy, Agave gives the entire squad a 2% ATK bonus for 15s per S-Energy over 10 she used.
Given that this skill has a 15s duration, Agave will always be at full S-Energy when it is used.
With Agave's passive +30 max S-Energy and her 4* or 5* weapons +20 max S-Energy, Agave has a max S-Energy of 100, meaning 20% of her S-Energy is 20 S-Energy.
Using 20 S-Energy means Agave uses 10 more than 10, so her Support Skill gives the entire team a 10 * 2% = 20% ATK buff.

Given that this is a 15s buff on a 15s CD, provided you spam it off-cooldown it's basically permanent.

ATK tends to get quite a few buffs (Logistics, Logistics substats, Manifestation levels, other support operatives....) and is quite a saturated category, but despite this, 20% ATK is a good bonus considering it's basically permanent and doesn't require much investment.
Agave also gives a pure-ATK boost, which almost every main DPS operative in the game benefits from.
Many other operatives like Celestial Swan, Nightglow, Starshine, Phantasia, Kaguya, Exuvia, etc. all have some restriction on who can use their buffs.

Provided Agave has her 4* or 5* weapon, she can provide this full 20% ATK buff, which is a very low barrier to entry.
(Without one of her signature weapons that increases her max S-Energy, it's still a 12% buff due to her +30 base S-Energy.)
Agave doesn't get any bonus to her Support Skill from her Manifestations, and her Neuronics and Deiwos also don't functionally change it, so Agave having her 4* or 5* weapon is all that she actually needs to be a decent support, and even without any investment at all it's again a 12% buff, which can benefit all operatives.

Is Agave a great support?
Not really - compared to other support operatives like Celestial Swan, Nightglow, Riptide, Kaguya, Starshine, etc., Agave does fall extremely short, but Agave provides a useful benefit with 100% uptime and zero investment outside of just having Agave and hopefully having one of her signature weapons.

Will Agave make it onto an endgame team as a support? Not unless Parts Breaking is needed, no.
What Agave will do though is provide an extremely easy-to-get buff that benefits basically all dps operatives, with 100% uptime, which is enough to make her an ok support for new players, or for newer players who haven'to put investment into supports yet.
I don't recommend you pull Agave unless you either like her as a character or need Parts Breaking, but if you are a new player and trip over her then she can potentially be a competent support.

Weapon

Snapshot Ace
Her 5*, and her best weapon.
Pure Verdure
Her signature 4*. Use this if you aren't using Snapshot Ace.

For many support operatives you might normally want to take a support weapon such as Lapis Lazuli that works when the operative uses their support skill, however Agave's signature weapons give her extra max S-Energy, which does boost her support skill directly. As such her two signature wewapons are not actually bad choices for support weapons.
Given that they're also her best weapons to use as a main dps and as a parts breaker, you can potentially just use them for her as a support as well.

If you do want to use her as an ATK support only, then there are other better weapons like Abyssal Light or Prismatic Igniter, but given that her signature weapons are also ok as support weapons for her, and that her support role can include parts breaking (for which her signature weapons are much better than the support weapons) her signature weapons can work out on top.
Similarly, if you are using Agave as a general support only then it's because you don't have any better supports for your dps, in which case your investment is better spent on other operatives, not getting Agave a second non-signature weapon.

Basically, just give Agave one of her signature weapons, even if you only want to use her as a support.

If you don't have either of her Signature weapons, then use whatever you have lying around that is highest-levelled - Agave really benefits a lot from her signature weapons, so it's not really worth putting lots of investment into another weapon for her, as you'll stop using that other weapon as soon as you can get one of Agave's signature weapons.

For Weapon Parts Agave generally wants max ATK.
Destructible Object Damage is also a great stat.
Which is better depends on how you use Agave - If only using her as a Parts Breaker, then Destructible Object Damage is her ideal stat.

Logistics

Use Chaya squad - it was designed specifically for her and is her best choice.

For stats Agave wants:
Basic Stats: +10.0% ATK
+106 Alignment Index.
Special talent: +8.5% Electrical Damage

ATK and Electrical Damage to increase her damage.

Skills can't crit, so since most of Agave's damage is in her skills, crit stats are not overly useful to her.
Similarly, Alignment Index gives skill damage, making it very useful, and her second best stat after ATK.
Due to Agave's constant skill spamming, Skill Haste is a good cope stat. Not as good as Alignment, but not the worst.
All other basic stats are useless to Agave.

If you only care about using Agave as a Parts Break, then all logistics stats are useless to her, as none of them actually affect Parts Break damage.

Manifestation

M1 decreases the S-Energy of her Standard Skill by 2 when at phase 2, 3, and 4. She also recovers 2 bullets per cast instead of 1.
The reduced S-Energy cost allows Agave to use her Standard Skill 1 additional time per rotation.
This is true regardless of whether Agave starts at Phase 0 or Phase 4.
Recovering 2 bullets per standard skill hit means that Vidya only has to shoot half as much, allowing her to use her standard skill more frequently.
Since her standard skill is where the vast majority of Agave's damage comes from, shooting less and using her Standard Skill more is a large damage buff.
Combining the longer skill-damage rotation and the lower downtime from shootingg, M1 is a huge damage buff for Agave.
M2 increases the Final damage of Agave's standard skill by 8/12/15/20% depending on its phase.
When used as a main dps for endgame content (i.e. bosses), Agave is pretty much only going to be using her standard skill at Phase 4, so it averages a maybe 19% damage buff for endgame content.
M3 allows Vidya to recover 3 S-Energy per shot, and decreases the targets DEF by 15% for 5s.
This increased S-Energy per shot again allows Vidya less downtime for her standard skill [to 2/3rds], and thus shortens her rotation, increasing damage.
The DEF bonus is a nice damage buff too.
M4 increases the level of Agave's standard skill by 1, increasing the damage of her standard skill by 10%.
Since almost all of Agave's damage comes from her standard skill, this is a very nice boost, but it is just more damage.
M5 increases the Final DMG of Agave's active skills by 0.1% per 1 Max S-Energy.
Given Agave generally has 100 max S-Energy, this is a 10% Final DMG boost to her skills.
Being a Final DMG boost makes this very strong, but it is only 10%.
Like M4, it's just more damage.

M1 and M3 are nice QoL buffs to Agave, whereas M2, M4, and M5 are just more damage.
As such, if you want efficiency (good damage without high investment), then M3 is a good stopping point.

Good Teammates for Agave

As a main DPS Agave really wants Skill DMG buffs or to debuff enemy resistances.
Whilst Agave does shoot her gun sometimes, it's weak, doesn't have an amazing RoF, and Agave doesn't fire many shots with it.

Good supports for Agave are:

Vidya - Celestial Swan
Vidya massive reduces the enemies DEF and Resistance, and buffs the teams damage a little too.
Vidya only debuffs the damage resistance of the damage type the enemy has most recently received.
As such, if using Celestial Swan, then make sure the other non-Vidya support isn't off-element to Vidya.
(i.e. They either deal Electric damage or do not deal damage at all).
Siris - Freefin
Freefin provides strong skill damage buffs, although Agave can't make use of Freefin's Wavehunt thermal skill damage buff.
Enya - Exuvia
Skill buffs are very nice for Agave, and she does regularly shoot her gun and do a lot of skill casts, allowing her to make good use of Exuvia's buffs.
Exuvia is also on-element to Agave, which is nice.
Marian - Aquila
Aquila provides very strong generic damage buffs, which makes her an excellent support.
Aquila is off-element to Agave (Aquila constantly deals Kinetic damage).
Yao - Nightglow
Agave can't make much use of Nightglows ballistic or crit buffs, but Nightglow's ATK buff is nice.
Nightglow is also on-element to Agave. (Nightglow deals Electrical damage)
Acacia - Kaguya
Kaguya is a good resistance debuffer - not nearly as strong as Vidya - Celestial Swan, but if you aren't using Vidya then Kaguya can be used as a much weaker substitute.
Eatchel - The Cub
A Blitzing Fangs Eatchel provides healing as well as a decent ATK buff, without dealing any damage herself.
Not the strongest support, but still good.
Marian - Riptide
Riptide gives some very nice Skill DMG boosts
The low duration of Agave's ult buff as well as the very short duration of Agave's weapon buffs can make Riptide difficult to fit in to Agave's rotation.
Note that Riptide is off-element to Agave (Riptide deals Chaos damage)
Mauxir - Shadow Ka
Agave's auto-aim means Mauxir's target utility isn't useful for her skills, but it can be useful for her gun, and the extra damage is nice regardless.
Note that Shadow Ka is off-element to Agave (Shadow Ka deals Chaos damage)

As a support, Agave works on any team that needs Parts Breaking.
She can also be used as a general support should you not have any other supports, since she works with almost all dps operatives.
As such, Agave can be used as a support on basically any team.