I was a winner at 2000NL, got my start by playing SNG's, built my bankroll from MTT's, and moved to cash games. I don't have much time to play anymore. When I do play, it's normally Heads up NL or LHE... Sometimes I like to find a table that's really shorthand with 2 or 3 players, and jump in. I'm an aggro action junky LAG, so shorthand/ hu's fits my personality/style better.
It is addictive! Are you playing NL or LHE, SNG's or MTT's?
Collusion mostly occurs in MTT's: players paying mules to make it through to a certain blind level before they hand over their account to a better player to finish the game.
Visit the 2+2 forums and read the instructional posts. Purchase pokertracker so that you can keep an accurate accounting of how much you win/lose, it also keeps stats on how you play, and how the players you play against play. Example- it can tell you how aggressive or passive you are from every position at the table, how often you fold, how often you open a raise, how often you call a raise. It can also help you avoid the good players, and realize who the bad players are. It's a must have, and it will help you improve your game. You can demo it for free. Also look into joining a training site like cardrunners, stoxpoker, and deuces cracked. There are other training sites that specifically focus on MTT's and SNG's.
Remember cash games are where the sharks prey on the fishies!!! MTT's / SNG are an easier place to start, and build a bankroll. I honestly recommend starting small and building up, not just depositing a lot of money, and playing with the big dogs. Why pay them to learn?
Have fun.