Lyfe - Infinite Sight (a.k.a. "Lyfe IS")

If you don't have her yet but want to try her out, Lyfe IS is available as a Trial Operative in Story Chapter 13 "Suspense in Skytopia" (Main Story // Journey // New Hentiro)
(Specifically; mission 13-4, and all missions from 13-7 onwards.)

Overall, Lyfe IS is a pretty easy operative to play, having high damage, high mobility, and high survivability, although her constant movement and dodge spamming can get annoying after a while, especially in small spaces, and her ult is basically useless against single-targets like bosses.

The Basics

Role: Main DPS
Deals Kinetic Damage
Weapon Type: Dual SMG
Deals both ballistic and skill damage
(but primarily ballistic damage)
Mobility is great

How to use Lyfe IS

Use her standard skill off-cooldown
If your dodge shot is full/charged, use it
(but reload first if you don't have the ammo for it)
Otherwise just hold down the trigger

Use her Ultimate against large groups only, never against single targets

How to build Lyfe IS

Weapon: Nightborne Crown / Revolving Glow
Weapon Parts: ATK
Logistics Squad: Nova
+10.0% ATK
+106 Alignment Index
+8.5% Kinetic Damage
Best supports:
Vidya - Celestial Swan
Fenny - Starshine
Yao - Nightglow
Tess - Phantasia

Standard Attack

IS' standard attack deals damage and also charges up her Dodge Shot.

Dodge Shot

When the gauge is full, IS' next dodge will be a Dodge Shot.
This will shoot 10 bullets extremely quickly, dealing high damage, always crits, and with auto-atm.
The base damage of her dodge shot is affected by her Crit Rate and RoF.

Most of IS' damage comes from her dodge shot - her regular shots don't deal much by comparison.
Dodge Shot suffers a massive damage penalty if IS doesn't have enough bullets to fully use it.
If IS doesn't have enough bullets to do a full Dodge Shot, then reload first so you don't waste its damage.

Lyfe IS' dodge is not an actual dodge - she can't be interrupted during it and gains 50% damage reduction, but is still vulnerable.
Nonetheless, her dodge is a large survivabiliy increase.
The dodge moves her in the direction IS is already going in. If stationary, she defaults to moving forwards.
This means that you probably want to keep IS moving, otherwise you'll just keep moving closer to your target as you spam her Dodge Shot.

Since it always crits, CRIT Rate buffs instead give her Dodge-Shot an equivalent amount of Ballistic damage.
Since it has a fixed rate of fire, RoF buffs instead give her Dodge-Shot an equivalent amount of Ballistic damage.

Standard Skill

IS' standard skill deals kinetic damage and marks an enemy with an Insight Mark, which fires an "Insight Ray" whenever Lyfe IS uses her Dodge Shot, dealing additional damage.
Shooting an enemy with an insight mark also causes IS to get extra Dodge-Shot charge per hit.

With her Neuronic, using IS' Standard Skill will fully recharge her Dodge Shot, so if her Dodge Shot is already full, use the Dodge Shot before using her skill.

Basically just spam her Standard Skill off cooldown.

The extra damage from using her Dodge Shot against a target with an insight mark is where a large part of Lyfe IS' damage comes from.
Again - most of Lyfe IS' damage comes from her Dodge Shot.

Ultimate Skill

IS' Ultimate Skill causes her to deal PBAoE damage over a massive radius.
This is absolutely fantastic for taking out groups, but it is a hefty DPS loss against single-targets, so don't use her Ultimate when bossing.
This does mean that against bosses IS doesn't need or want U-Energy, allowing a support operative to make full use of it.

In terms of damage breakdown, for me my Lyfe IS does around 15% of her damage from her actual shots, around 60% from the shots from her Dodge-Shots, and around 25% from her Insight Rays.
This means that around 85% of her damage comes from her Dodge Shots, with only 15% coming from regular shots.
This also means that the vast majority (around 75%) of her damage is ballistic, with the 25% from her Insight Rays being Skill damage.

Weapon

Nightborne Crown
Her signature 5*, and her best weapon.
Like most modern 5* weapons, the "enemies take more dmg" is the strongest part of this weapon, and make it very strong.
Revolving Glow
Her signature 4*.
Basically just a weapon version of her 5* with weaker numbers.

Her 4* and 5* play identically though.

Whilst Lyfe IS was originally the only Dual SMG operative, since the introduction of Bubu - Specular Soul there other now Dual SMGs in the game, but Nightborne Crown and Revolving Glow are the only 4* and 5* Kinetic-damage ones (Bubu's are Chaos), so if you don' have either of Lyfe's signature weapons then use the default 2* weapon she comes with (Optimal Solution) as that also deals Kinetic-damage and its ATK buff is useful, which make it the next best Dual SMGs for Lyfe IS.

For weapon Parts Lyfe wants Crit Rate, ATK, and RoF.

Logistics

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

For stats you want 10.0% ATK and +106 Alignment Index.
For the Special talent, you want 8.5% Kinetic Damage

Alignment gives her more Final Damage for her Dodge Shot, and is her best second stat (after ATK)

Crit DMG isn't too bad, as her dodge shot (where most of her damage is) has a 100% chance to Crit, but doesn't affect the Insight Ray damage from her standard skill.
Crit DMG is thus a decent cope-stat though if you have a good roll for it and don't want to spend the resources to re-roll it.
Since her dodge-shot always crits, crit rate only affects the crit rather non-dodge-shots, which are a minority of her damage.
Crit Rate buffs do give an equal amount of dodge shot damage.
This means a max-roll crit rate mod gives +5.3% dodge shot damage, whereas a max-roll alignment index gives dodge shot +10.6% damage buff - literally twice as much.

Manifestation

M1 increases the Final DMg of her Dodge Shot by 20%, as well as making her dodge shot not reduce stamina.
Her Dodge Shot not reducing stamina is a very nice QoL feature
Most of Lyfe's damage comes from her Dodge Shot, so a 20% Final DMG bonus for it is still a large increase.
M2 Lyfe gains 20 Dodge-Shot Charge after she Dodge Shots
Since a Dodge Shot takes 60 Dodge-Shot Charge, this allows her to need to only gain 40 charge to Dodge-Shot not 60, for a 1/3rd damage increase for her Dodge Shot.
M3 gives Lyfe 12% more Ballistic DMG to targets with 1 insight mark. For each extra insight mark increase it by an extra 3%.
Insight Mark has an 8s cooldown and a 10s duration, so an insight mark should always be active.
M4 increases Lyfe's Standard Skill level by 1, increasing its damage, as well as increasing the additional damage Lyfe IS' Dodge-Shot to an enemy with an Insight Mark.
The extra damage is a 10% increase.
M5 gives Lyfe IS 20% increased Kinetic DMG when equipped with a Kinetic weapon (I.e. hopefully always)

All of Lyfe IS' Manifestations increase her damage by a decent amount.

If you want efficiency (good damage with minimal investment), then I'd say M3 is a good stopping point.

Good Supports for Lyfe - Infinite Sight

Lyfe IS works well with most of the games stronger [ballistic] support operatives:

Vidya - Celestial Swan (and other resistance shredders)
Celestial Swan and other resistance shredders (Acacia - Kaguya, etc.) that reduce the enemies resistance help enemies take more damage.
If using Celestial Swan, make sure the other support isn't off element to the main DPS.
Fenny - Starshine
Starshine provides IS with strong ballistic buffs, and utility of not having to reload is useful.
Yao - Nightglow
Lyfe IS can make full use of Nightglow's ATK, Ballistic, and crit buffs, and Nightglow is a fantastic support for Lyfe IS.
Note that Nightglow is off-element to Lyfe IS (Nightglow deals Electrical damage).
Tess - Phantasia
Phantasia adds Frost Damage to each shot. Given that Lyfe IS has a high fire rate this adds up to a lot of damage.
The increased ballistic damage of Tess' ult is also nice.
Again - Phantasia is off-element to Lyfe IS (Phantasia adds Frost damage) and adding it per-shot means Phantasia and Celestial Swan are utterly incompatible for IS.
Eatchel - The Cub
A Blitzing Fangs Eatchel provides healing as well as a decent ATK buff.
Not the strongest support, but still good.
Mauxir - Shadow Ka
Her Dodge-Shots auto-aim means that Lyfe IS doesn't care that much about the utility of not having to aim, but the extra damage Mauxir offers is nice.
Note that Shadow Ka is off-element to Lyfe IS (Shadow Ka deals Chaos damage)
Enya - Exuvia
Lyfe IS shoots at a very high rate, and her Insight Marks fire very frequently, allowing Exuvia's Zephyr Machine to proc quite often.
Note that Exuvia is off-element to IS (Exuvia deals Electrical damage)