http://gettie.i2p/posts/osu-on-linux.html
Also, I suggest using the offset wizard (click here to read the guide about it) in order to set up the game properly. Conclusion I know that this guide is not the best for some people, because it seems too much of a hassle to set up a game on Linux. For those people, the best option is a Windows and Linux dual-boot system, or a completely different PC just for games.