1) Griffindor Common Room: Very easy to beat, not a bright player if you are having problems see below.
2) Great Hall: Somewhat easy, but a challenge. See below if you are having problems.
3) Library: Good player, hardest to beat. See below if you are having problems.
If you are not good at chess, go to chess.com, put it on hard, play as black and do exactly what the computer does as white. Make sure that your moves on the computer match what Black does in the game, this will help you win a lot faster.