At Microgaming casinos, you can play slot tournaments daily. Such tournaments is all about getting the top 3 places to win money. The highest deposit is $25 and in such games you can win 50.000$. You first deposit money in your casino and then click on your desired casino tournament and click "Pay the fee". There are many different games to play in different slot tournaments. Before when they first came out 10 years ago it was much easier to win as the number of players were less, today it is harder but still worth a shot.
You should restart your PC before playing as to maximize speed of casino rounds. Except of this there is not much else to do than pay the intro amount and spin as fast as you can to get the top prizes. NETentertain casinos offer slot tournaments but not daily, rather once a week or so, depending on each casino.
Good luck on your slot casino tournament!