-I think I am doing poorly farming because I can't afford haunting guise as early as I want.
Well, getting the gold earlier and earlier is the biggest thing you can strive for at least in your early game. Being able to get that much stronger earlier can change a lot about the game since it makes it easier to shut down your lane opponent and do things around the map. Basically, work on csing :x
-I was reccomended to go Zhonya's first, but I am drifting towards getting the revolver and guise after 1st tier boots.
I don't think that Revovler is all that good on Kat. You're better suited with Haunting Guise -> Abyssal* rather than a Revolver. Revolver -> Spectral Wraith isn't that bad though but I personally don't find the Spell Vamp worthwhile on Kat's kit when you can just spare the gold for a potion or two in the early-to-mid game rather than itemize it.
Plus, Gunblade isn't that good either so it doesn't feel all that efficient.
*Or early Seeker's if vs an AD Mid. Haunting Guise -> Sunfire Cape works well too vs ADs if you want to go the far tankier route. Early Zhonya's isn't ideal all the time unless you're expecting to be going in a lot.
-I'm comfortable with Q-E-W, but not the disengage, especially with casters and ranged. i get damage in, but depending on who I'm fighting, they can turn around just as quick and deal equal damage.
With maxed W first, you tend to disengage faster than most people can DPS. It's especially noticeable on skillshot based characters. It's not something you can always do (because of things like Teemo, like you mention) but it's a pretty vital skill to have when playing Kat: Being comfortable enough to jump in and W for free damage.
...of course, sometimes doing that in the mid-to-late game will have someone interpret it as an engage so sometimes it backfires!
Well, any other details? Low level games tend to just stalemate on team fights because nobody wants to initiate so that's usually where things collapse. While Kat isn't ideal at initiating, being able to start a teamfight on your terms can generally win games anyway so that's something to keep in mind. At the very least, know what to look for as a good time to initiate (and then initiate and your team /afks).
From what you've written so far, it doesn't really seem like you were playing bad so it's probably just people looking to scapegoat someone. Of course, at the same time, you can't be super passive either and if you only look for free options, you're wasting your potential. While it's nice to chip away and stay back, you can't do that forever without having a comp meant for it (e.g., Jayce).
Basically, don't go super balls deep as Kat unless the situation calls for it but don't sit back until that moment arrives. Try to create those situations and be sure to punish mistakes (improper positioning mainly). Waiting around won't win you games. If nothing else, learning your limits happens a lot easier/faster when you play aggressively.
Today I have been doing a bit better.