what would be a good build for it?!?
The Search function on the forums here may be eternally busted, but Google still works - since this question has been answered 100x already in much more detail than people want to type out on demand:
© 2013 Riot Games, Inc. All rights reserved. Riot Games, League of Legends and PvP.net are trademarks, services marks, or registered trademarks of Riot Games, Inc.