This is my preferred [Garuda] build, swapping Blood Altar for Gloom to more suit [Garuda]'s active and mobile playstyle.

Gloom does not need to be maximised for range and strength, as [Garuda] is perfectly tanky with U.Fiber, [Quick Thinking] and [Primed Flow]. [Adaptation] is preference, and not necessarily needed.
Gloom is only slotted as it provides more efficient passive healing as Blood Altars % health healing is not too valuable when [Garuda] does not run health mods.

YOU ARE WELCOME TO CONTINUE USING BLOOD ALTAR IF YOU PREFER IT, I SIMPLY CHOOSE GLOOM AS IT BENEFITS MY PLAYSTYLE MORE.

With these mods, [Garuda] has effectively 6175.4 effective HP counting [Quick Thinking]. When Arcane [Guardian] is procced, this goes up to 11395.4.

Feel free to invest a second Umbral Forma to use a Rank 0 [Combat Discipline], I don't believe this to be necessary though. If you don't have Arcane Avenger, feel free to slot [Brief Respite] for the extra survivability over [Combat Discipline].

You can save your Umbral Forma if you choose not to run [Primed Sure Footed], but [Garuda] works especially well with AoE Weapons, so I recommend it.

THERE IS A MISCONCEPTION THAT GLOOM NEEDS TO BE MAXIMISED WITH STRENGTH AND RANGE, WITH NEGATIVE EFFICIENCY ON [Garuda]
This is not the case. Though it does work, it is less tanky than this build, and enemies inside nullifiers will kill you before you even see them. [Garuda] is perfectly tanky with [Quick Thinking] and Armor investment. Gloom, in this build, functions more as an alternative heal to Blood Altar, the slow it provides is merely a side-benefit and not what you want to build around.
Negative efficiency is a viable option, and you are welcome to swap mods around to fit [Blind Rage] if you so desire, but I personally found it less enjoyable, as you have to spam 3 a lot more, and charging her 1 at all drains your energy in seconds.

TIPS

• The basic 4 1 combo scales up to just about any level of content the game can throw at you, though in steel path I suggest using her 1 twice before throwing it, or charging it for a bit over a second.
• [Garuda] is perfectly capable of running most gamemodes without weapons, in higher level missions such as steel path, it may be beneficial to bring a weapon that can mass apply viral to groups of enemies to make her 4 1 combo kill more effectively.
• Her passive applies to all damage, similar to Rhino's Roar.
• [Garuda]'s biggest flaw is her inability to damage acolytes, they are limited to only 4 status procs of every type, so its near impossible to throw her 1 after her 4, as her 4 will immediately proc the max amount of slashes, and your companion will likely keep it capped. Due to this, I suggest bringing a weapon that can deal with Acolytes.
• If you want to replenish your shields for Shield Gating, and you aren't running [Brief Respite] and Augur Mods, remember that you can use your [Dread] Mirror to block all frontal damage, and also that your sheilds will replenish when you are invulnerable with her 1 and 4.
• Throwing her 1 will remove your Dread Mirror, so be careful, and make sure to jump with 1 again to get it back as soon as you are able.
• Don't focus too hard on your health bar, even at 2 health you still have a reservoir of energy that acts as a secondary health bar. A full energy bar is worth 4.8x more than a full health bar. Don't panic if you see yourself low health, if your energy is low too, try to hit someone with anything, even a charged 1 into a few enemies, even without 4 should be enough for a full heal with Gloom up, and you can use that to get your energy back.