Siris - The Goldfish

Siris - The Goldfish is not currently available as a Trial Operative in any story mission, so if you don't have her the only way to try her is to wait for her banner so she has a trial.

As a dps, Siris is a bulky but quite low-damage operative with average mobility.
As a support, Siris is basically useless until she gets her M2 buff which can sometimes give ballistic shots extra damage, although by the time you get Siris to M2 you'll likely either have 5* operatives to use instead, or you'll have made a proper team out of 4* operatives, which likely won't include Siris due to her low damage.
If you find her fun or just like Siris, then The Goldfish can work as your main DPS until you get a 5* operative to replace her with, but even among the 4*'s she's not great.

Overall

Role: Early-Game Main DPS
Deals Kinetic Damage
Deals ballistic damage
Mobility is average.

How to use Siris - The Goldfish

As a DPS:

Spam her standard skill as often as you can
Otherwise, just shoot stuff.

As a support:

If her support skill isn't active, use her support skill.

How to build Siris - The Goldfish

Weapon:
As a DPS: Tiny Grains / Full Alert
As a support: Lapis Lazuli
Weapon Parts: Max ATK
Logistics Squad: Twilight
(Amano-Iwato also good if using Siris as a dps)
Basic Stats: +10.0% ATK
+10.0% Max HP
Special Stat: +8.5% Kinetic Damage
Best squadmates:
With Siris as a DPS:
Fritia - Little Sunshine
Yao - Quiet Quitter
With Siris as a support:
Lyfe - Wednesday
Fritia - Little Sunshine

Standard Skill
Siris gains a blesing that gives CC-resistance and 25% reduced damage taken, which lasts for 10s.
If Siris dodges during the blessing, she gains extra Kinetic damage to her next shot.
With its first Neuronuc buff, the shot also gains +50% Dmg dealt to shields, which is a large bonus against shields.
With its second Neuronic buff, dodging also reloads 1 shot.

This has a 15s cooldown, but it goes on cooldown when the 10s blessing ends, so it lasts 10s every 25s.

The extra damage from this skill isn't particularly high, and the requirement to dodge every single shot means it really isn't much of a dps increase at all.

Note that the damage-per-shot is potentially higher than the damage-per-shot from the support skill of Fritia - Little Sunshine (Fritia is 9%, Siris can go up to 11%)

Note that the damage-per-shot maxes out at about the same amount that Fritia - Little Sunshine's does (11% ATK +27 for Fritia, 11% ATK +42 for Siris)

Ultimate Skill
Siris creates a dome that provides dmg absorption, increased movement speed, CC-resistance, as well as repelling enemies for 10s.

With its first Neuronic buff, when the dome ends it restores HP equal to 20% of its remaining shield.
This is a very small heal.

Siris' ultimate skill doesn't do any damage, and is basically useless for healing you, so there's basically no reason to ever use it.

Support Skill
Siris deploys a cover in front of her to block enemy fire.
It is neither a Shield nor an Auxiliary Unit.

The cover has very high HP, and can take a lot of damage.

Since it doesn't actually boost your operatives damage at all, Siris' support skill is generally not very good.
If you do actually want more survivability, you're better off taking an actual healer like Yao - Quiet Quitter or Chenxing - The Observer rather than Siris.

Manifestation

With M1 When Siris' support skill ends, it automatically uses her standard skill, but doesn't grant the damage buff when dodging.
This is quite a good survivability buff. If you want survivability you're still better off taking a dedicated healer instead of Siris though.
M1 doesn't buff her damage at all.
With M2, whenever an operative shoots through the cover from her support skill, they have a 30% chance of gaining the damage buff from her standard skill.
This is a decent damage buff, and the higher the operatives rate of fire, the more damage Siris can add to them.
This means M2 Siris can potentially add a lot of damage to certain high-RoF operatives.
Almost all of Siris' value as a support comes from the damage her M2 gives to shooting through her support skill.
M3 increases the amount of damage Siris' support skill can absorb by 50% of Siris' max HP.
Given how much HP Siris has, this is a large increase, but again - it doesn't increase her damage.
M4 increases the level of her standard skill by 1, and increases the damage bonus it gives.
The damage bonus is still not overly high.
M5 removes the time limit on Siris' support skill, so it only ends once it runs out of HP.
This allows Siris to maintain 100% uptime on her support skill if you can avoid it taking too much damage.
Having higher uptime on her support skill does increase the amount of damage her M2 gives.

Overall, Siris' Manifestations are very defensive, and don't increase her damage by that much, however with at least M2 Siris can increase the damage of your other operatives quite well, and with M5 [and without taking too much damage] the very high uptime on her support skill allows her to effectively act as a permanent damage buff for your shots.

Being a 4* operative, you'll get all her Manifestation buffs eventually.

Weapon

If using Siris as a main DPS:

Tiny Grains
Tiny Grains is Siris' best weapon.
Siris doesn't have any effects that require her to be in melee range or to take damage, but being a 5* Kinetic shotgun is enough to make this her best weapon without its proc.
Since Siris has a lot of HP and gains a lot of damage reduction effects, she can happily spend time in melee range to proc Tiny Grains' proc for more damage.

If Siris doesn't have Tiny Grains, then use whatever 4* Kinetic shotgun you have: Full Alert, Mechanized Cop, Precious Baby, etc.
Siris wants ballistic and kinetic damage buffs, but there aren't any 4* shotguns that change how she plays - just a bit more damage for some.

If using Siris as a support:

Lapis Lazuli
Lapis Lazuli gives an ATK buff for 15s after using her support skill.
Siris' support skill has a 20s cooldown, so you might want to give her some Skill Haste if using Lapis Lazuli, but a 15s buff on a 20s cd is still good.

For weapon Parts, Siris wants maximum ATK, as the damage buff from her standard skill is based on her ATK.

Logistics

The Goldfish is a 4* operative and is completely outclassed by 5* operatives.
As such, please don't waste logistics re-rolls on her.
Similarly, if you have the resources to get her a new logistics set, then you should put that investment towards your 5* operatives if you have any.

If using Siris as a main DPS, then consider:

Twilight
Reduces the targets resistance after dealing damage with a skill.
By-default Siris' support skill doesn't deal damage and hence can't proc this, but if Siris has her M2 then her support skill does deal damage and can proc Twilight.
The per-shot bonus from dodging with Siris' standard skill active can also proc Twilight.
Amano-Iwato
Gives ballistic damage, and a stacking ADS ballistic damage buff.
Since Siris spends most of her time in combat shooting stuff, Amano-Iwato is her best logistics squad for increasing her damage.
Amano-Iwato is a good logistics set for increasing Siris' damage, but Twilight works for Siris as both a DPS and as a support, whereas Amano-Iwato only works as a dps.
As such, Twilight is generally the better set, as it allows Siris to work as both a dps and as a support.
There isn't much point in re-rolling or givign Siris two logistics sets, as she is only a 4* operative.

Stats:
+10.0% ATK
+8.5% Kinetic Damage

ATK and Kinetic damage to buff her damage.

Siris wants maximum ATK, as the damage buff from her standard skill is based on her ATK.
Kinetic damage also buffs her damage.

Alignment Index gives Siris more HP (up to +3.18% HP per max-roll Alignment Index stat) but Siris doesn't really need more HP, and Max HP is better than Alignment Index at increasing Siris' HP anyway.
Given that there aren't really any other logistics stats that Siris benefits from, Max HP does work well for her.

As a support, Twilight also works well for her, since she'll likely be spamming her support skill somewhat often, although no logistics set works amazingly with Siris.

Given that Siris is a 4* operative and 4* operatives aren't worth wasting re-rolls on, it's fine to just go for ATK only, or to just give her a logistics set and not worry about what stats is has - you'll stop using her very quickly anyway once you start getting 5* operatives.

Good Teammates for Siris - The Goldfish

As a DPS:

Fritia - Little Sunshine works well for buffing Siris' damage, as each pellet of Siris' shotgun procs Fritia's buff.
Yao - Quet Quitter works well as a healer for Siris

As a support:

Any operative that deals ballistic damage at a high rate works well with Siris once Siris has her M2.
Since the cover from Siris' support skill is entirely static, operatives that can stay at range work well.
As such, Lyfe - Wednesday and Fritia - Little Sunshine are generally the best dps 4* dps operatives for Siris to support due to their high rates of fire.
(Fritia's buff buffs every shot, whereas Siris' is only a 30% chacne to buff each shot, so it's better to have Fritia support Siris than to have Siris support Fritia.)

Operatives that get into melee range can often find it easy to shoot through the shield work too, in which can Fenny - Lionheart and Nita - Hands also work well with M2 Siris.

If you have 5* operatives, then you should generally use those instead of 4* operatives like The Goldfish, however Katya -Rhapsody works by deploying her own barrier in front of her just like Siris, and Rhapsody has a tremendous rate of fire, meaning that M2 Siris does work well with Rhapsody should you not have any better 5* support operatives like Tess - Phantasia to use with Katya.
Note that Katya can redeploy her own skill to move around, whereas Siris' is stationary, so Siris' support skill will limit Katya's mobility.