Filaments - it’s not just the tier - it’s the type. Do a search for “calm” in the market and read up on the various filament types first. Each have a pro/con which lend themselves towards different type of weapon systems. The difference in tiers represents a higher level of difficulty and lower survival rate (T4 and T5 filaments also give you suspect status on exiting in high-sec).
Next, read this article and familiarize yourself with the various NPCs you’ll be facing.
For the Gila - Gamma, Gamma, Gamma… You don’t want to run Dark or Firestorm filaments with that fit. For starters, your drones won’t be able to hit anything in Dark filaments without a dual web - and doing so nerfs your passive tank. Firestorm filaments weaken your thermal resistance (already weak) and double the armor of most enemies.
Gamma filaments double your shield hit points - which is a massive boost to your passive tank (and thus why the Gila + Gamma filaments are the most popular combination). It also doubles the shields of NPCs - but most NPCs have strong armor and weak shields.
For drones you only want Caldari Navy Vespa. That’s it. They have the highest tracking and shield regen rate which means they can survive both fire from NPCs and the anti-drone defenses in the Abyssal pockets. For missiles, skip Precision and stick with Faction and Fury. I find Inferno works best unless you’re running Exotic filaments (which weaken kinetic resistances).
Stick to T1 calm and T2 agitated filaments for starters until you familiarize yourself with the Abyssal mechanics. Starting in T3 and up you’ll get neuted often and may find that you need to switch to an active tank that includes a cap battery and shield booster. There’s one or two active Gila fits floating around the forums (try “Gila” and “Abyss”).