Cash games on big sites are for pros, and its very hard to beat, but good to try playing cash on obscure poker rooms which focus more on casino , and you might find bad players there. I started playing on a Croatian poker room where there are just 10-15 players online.... and a daily freeroll with 100 players
Everyone is bad

and I won't mention the name because I don't want traffic there .
Playing tournaments is the best way to go because you apply the same rules for every buy-in from 5$ to 10000$ (because on buy-ins less than 5 you can still encounter bingo players)
The rules to follow are simple:
Play tight early , just top 20%
hands and from position. Choose your spots ! Fold preflop small pairs and marginal hands like KJ off and 9Qoff when there is a 4bet or to many players in the pot
In middle game start playing top 25-30% hands because you must steal some blinds.
On the bubble play tight again, and if you are running deep , put pressure on small stacks
In the money try to have an average stack, and always shove good hands when under 15BBs
Side rules
- always play strong hands against loose players (you can't
bluff a calling station)
- Steal blinds from tight players with 2x BB bets ( and fold if they 3-bet , because they are strong)