Your a little all over the place at the moment. Sort of need to pick a direction.
For a budget deck I recommend:
Abyss is both one of the most expensive and difficult to play factions, baring some aggro variants, but they are a ton of fun and very rewarding, and of course my favorite aesthetic choice. But lucky for you Swarm is one of its few budget friendly options.
To upgrade the deck there are a couple big starting Abyss crafts. Desolator goes in and makes allmost any abyss deck better. Revenant also goes in most decks allthough swarm is one of the few that can skip it. And if you are commited to swarm then Soul Grimwar and or Cresendo are a must. After that the bloodborn set gives you access to the furosa/crypto combo, and maybe Variax as an alternate way to play.
I have a ton of Abyss decks as well as the rest of my here:
Plenty of directions to build towards over there.