This is my Infinite [Gara]. With this build, you can infinitely scale your damage and kill anything in your way with ease.
In My Aura, I have [Steel Charge]. This is to further boost my stat stick, but if you want Corrosive Projection or Energy Siphon, and can forma that slot to a Dash, but that would require another Forma.

Break Down

1st-Shattered Lash

[Gara] lashes out with a stream of glass. For this build to be successful, you will need a stat stick for her 1st. This is pretty much a Melee weapon that is modded for use by a "Suede Exalted" Warframe ability. Here is a good example of A Stat Stick. Any weapon can be a stat stick, but the best stat stick is one that has a Syndicate mod with damage or an elemental, but you also want a high Riven Disposition so that you can get a really good riven. Her 1st is essential but I'll explain why later.

2nd-Splinter Storm-

[Gara] creates a bubble of splintered glass around her that can give you up to 90% Damage Reduction at 129% power Strength. This is essential to [Gara] and the rest of her kit. Splinter Strom also does damage and this damage scales infinitely, I'll tell you how later.

Spectrorage-

[Gara] Creates a ring of mirrors that enemies shoot at and when the mirrors are destroyed they deal damage. This ability is honestly terrible and I don't recommend using it. It does have an augment that gives you more energy, but that takes up an extra slot, and using Zenurik Focus School is much better overall.

Mass Vitrify-

[Gara]'s lets out a ring of Molten Glass that spreads out in a circle and hardens once it has finished growing. This is how her damage scales. This is simply a large defensive ring, however, it is broken into segments and these segments have individual health pools. These Segments deal damage when destroyed, but you can also destroy the entire ring with her 1st and deal good damage in the area around the ring.

How to Play

Here is how you play [Gara] to [Reach] her fullest Potential

1. Cast her 2nd, Splinter Storm. You must keep this up at all times, however, mass vitrify refreshes the duration

2.Cast 4th, Mass Vitrify

3. Move outside of the rind and cast her 1st while looking at the ring. The ring will explode and in the bottom right, you will see your damage numbers. By Repeating this you can infinitely scale her damage

4. Repeat 2 and 3 until desired damage, however, you must keep up her 2nd in order to maintain damage, so if you're not going to increase your damage you still need to do steps 2 and 2 once her 2nd is close to running out.

5. Once you have Reached desired damage, you can walk around, and enemies 4m of you will take damage from her 2nd.

Like this, you can do literally any mission in the game, but remember that she will do best in missions like defense and survival, so if it is something like a capture, I would just recommend using your regular weapons.

Focus Schools

Although I have some Decent Efficiency, your energy will not last for a very long time, Especially when you are building up her damage. This is why I would recommend Zenurik for Energizing Dash. Since we are not using a Normal Melee, Naramon is unnecessary and even then, Zenurik is still overall the best School

For Arcanes, anything goes. I would recommend Arcane Energize and Arcane [Guardian]. More Energy is always helpful and Guradain means even more survivability, but take into account that this is Warframe, and my builds are just a suggestion. Use whatever helps you out the most and what you enjoy.

Helminth

As mentioned earlier, her 3rd is kinda garbage, so if you're looking to helminth, that is what you should replace. Because of how [Gara] is played, I would recommend a grouping ability like Ensare from [Khora], or Larva from [Nidus]. Ensnare is the better of the two but definitely the much harder to get one.

Go Kill Everything Tenno, Enjoy