Sorry, but any Squigalanche, isn't a competitive list for do a 3-2 in any big tournament. A good record with this type of list is a 2-3, and this is because after losing a few games you're gonna play with others lists that they aren't competitive too.
The list have this problems:
- Too many Manglers. They're fine, but they aren't Maw-Krushas or Terrorgheists.
- Boingrot are very slow, they can't do the job of fast cavalry.
- You have very few models and the save rolls are awful, and it's easy you lost half of your army versus Kharadron, Seraphon or Cities of Sigmar. You are going to have too many problems to capture objectives.
- Loonboss on Giant Cave Squig are mediocre support heroes. After you charge with your units his job is finished and he's going to die or move around the map without doing anything
If you want to improve the list, stop trying to play the Squigalanche, remove some Manglers, add other things like a Webspinner Shaman on Arachnarok, Sneaky Snufflers, Stabba+loonboss, Rockgut Troggoths... Try to make a mixed army and try to play around the objectives.
Squigalanche is one of the worse glass cannon actually, Idoneth, Khaine, Tzeentch, Seraphon are going to crush your army so easily, and you aren't enough strong to beat Bonereapers, Orruks or Chaos Ascendant.
Here you have a good review, I think is the best review of the Gloomspite Gitz army in youtube.
I'm not 100% agree with all the things he says or the competitive lists he show us, but it's a goof point to start.