Hello and welcome!

This has been my comfy [Gara] build for quite some time now. Especially with the new changes to her shattered lash and mass vitrify.

Helminth!!!

Nourish replacing [Spectrosiphon].
Explanation:
Nourish with sufficiently high power strength allows us to run a fully efficiency negative build and not suffer from the horrendous energy drain cost that Gara usually incurs.
Added bonus in that the viral bonus damage makes our 4-1 combo stronger by including an additional damage source for its calculations.

Arcanes!!!

When it comes down to arcanes there is quite a lot we can do on this build.
My standard I have included in the above slots.
Molt Efficiency- There are very few avaliable slots for us to put additional duration into the build, and most mods only give up to +24% duration. We dont want to use the corrupted duration mod as we need our range more. +36% duration is a huge QoL and impacts nearly every ability you have.
Molt Augmented-You will be doing huge room wide AOE clearing destruction so +60% free power strength is always appreciated.

However, aside from these, there are some very fun unique synergies I'll mention below. I will sort these by rough categories.

DPS increase/Raw damage/Power strength---
Take these when you want to amplify your TTK and overall damage output for the build.

1. Arcane Avenger-This works very well with Combat Discipline and has the added bonus of allowing your innate shatter lash to crit. (not the 4-1 combo, just the 1 cast itself) AZNinvations has a very indepth guide on this on youtube.
2. Molt Vigor- +45% power strength when you pop in and out of operator. Pairing this with Zenurik for energy sustain (the passive energy [Regen] is extremely amplified by means of nourish) and its bubble upgrade grants +20% additional strength on top of that while remaining in the energy zone.
3. Arcane Blade Charger-This one makes quite a lot of sense. Primary kills amp your melee damage which in turn amps your shattered lash scaling. Not much more to say about this one.
4. Arcane Arachne- In the same vein as Arcane Blade charger, but guaranteed to proc and amplifies all of your weapon damage, not just melee, and isn't reliant on getting a kill first with your primary. Honestly the wall latch aspect is something you'll be doing all the time as you try to get into the perfect positions of verticality to hit as many enemies as possible with your Vitrify.
5. Theorem Demulcecnt If you have a kitgun, this can be utilized to amplify your weapon damage as well.

Utility, energy economy, survivability---

1. Arcane Energize-If you dont yet have nourish this mod can be extremely helpful in energy management but is also VERY expensive unless you also are adept at farming Eidolons.
2. Arcane Steadfast- Again, energy shouldn't be an issue on this build but it can be nice to have free casts of your skills.
3. Arcane Ultimatum- You shouldn't need too much in the armor department with your Splinter Storm 90% DR, but due to [Gara]'s passive constantly blinding foes and opening them up to finishers this arcane is very easy to proc.
4. Arcane Trickery- In the same vein as Ultimatum, but you become invisible instead.

Archon Shards!!!

I have this build with 4 Crimson archon shards and 1 tauforged azure but they aren't strictly necessary. I'll go over a few best in slot choices for Gara for each color.
Crimson-
Base Power Strength- Slotting more power strength should be your main priority with Gara. 2 Tauforged (if you're lucky enough) completely offsets the negative from the Overextended mod.
Ability Duration-In the same vein as I explaiend why we take Molt Efficiency, you may instead slot more duration as a shard. I suggest saving this for a Tauforged and only slotting 1 but the arcane gives much more of a bonus (36% vs 10/15% duration) you would need to slot 2.5 tauforged to overcome the arcane slot's bonus. It's better to go for Strength.

Azure-
Bonus to Armor--Scales her vitrify walls E-HP as well as making you gara much tankier.
Bonus to Max energy--If you want to take this, you may, but it only ads 50/75 max energy. You would need to invest too many of these to offset the mod slot of primed flow.

Amber-There are higher priorities for Crimson shards, but if you have them laying around slot them!
Cast speed
Energy filled on spawn
Efficacy on Energy orbs

Focus School!!!

We go Zenurik here for energy refill ability. It also has the added benefit of the +20% power strength aura while in bubble which you will be utilizing often.
If you are more versed in energy managment or have lots of E-pads or are going to be queuing with a team and known abilities like dispensary, etc and dont have to worry about your energy generation method, Madurai is more power strength (+40% after sling).

Optional/Flex Mods!!!

1. [Primed Sure Footed] in exilus slot. Replaces [Power Drift].
2. Any other mod you want in place of [Shattered Storm] if the content you're doing is dying instantly, ergo under steel path tier.
3. For smaller tilesets you can opt to drop Overextended and instead put Adaptation or any other D polarity mod of your choosing in its stead.

Buffs/Playstyle!!!

For those who are unaware, the dev's gave [Gara] a much needed quality of life patch for her rotation of abilities. These were released I believe along with [Citrine].

1. You no longer have to go outside the ring to build stacks of your splinter storm.
2. All enemies caught inside the ring (as well as the usual enemies outside) are affected by the damage pop of your 4-1 combo.
3. Introduced [Shattered Storm] augment for her 2nd ability.

This second change is why we opt to run our build with lots of range. High range not only allows our Vitrify to affect more enemies per cast, but also increases Nourish's retributive damage AOE as well as ur splinter storm's touch of death cloud. A win-win across the board. Remember, enemies affected by 4 also are more vulnerable to damage. With high enough strength which this build easily reaches, you can make all enemies take upwards of 3x more damage. This of course directly scales into the amount you can scale your splinters. while this isn't specifically a touch of death build, its nice that we can still utilize that aspect of her kit whilst still being a tile-wide room nuker.

Why Shattered Storm--

Most people were underwhelmed in that the [Shattered Storm] augment would not spread the theoretical millions of damage to all enemies around them (that would honestly be insanely broken)
instead dealing only the base damage of the ability on cast. However this is not where the augment shines. With the new change to her vitrify, automatically spreading her splinters to all enemies not instantly killed by her Vitrify is a huge multiplicative boost to your overall DPS approaching nearly 2x multiplier of all damage (this is on TOP of the nearly 3x multiplier from Vitrify). This damage vulnerability effect is only occasionally used by [Gara] mains to make particularly tough targets easier to take down but casting it on every enemy to get maximized utility out of that multiplicative bonus is counterproductive and energy inefficient. This mod solves that. Even more beautifully so in that it solves it in part of a skill rotation combo we would be doing already. I cant say enough nice things about this augment. Its fantastic.

[Combat Discipline]+[Mending Splinters] Augment:

These two mods interact beautifully together. Not only is [Mending Splinters] phenomenal for maintaining the health integrity of defense objectives (looking at you Void Armageddon, and arbitration) it also serves as the method in which we have a near permanent uptime on our arcane intensify granting us +60% power strength. (vs Umbral's 44/55/77%) The health loss is mitigated by your 90% damage reduction from splinter storm so you end up never actually harming yourself. Not only is this 2 mod combo more capacity efferent, it allows us to bring other mods that strengthen our kit as opposed to being required to bring 3 umbral mods.

This build will not include her stat stick as there are already plenty of those already. But suffice to say that nourish also provides viral proc damage for damage calculations.
Damage=Good
Crit=bad
Innate base combo=good
attack speed=irrelevant
slash or puncture mods=strengthens the 1 on the style used. (slash or puncture)

And that's about it. Go forth and show the world that there are 2 queens of warframe!