Best champion on bronzes?

Garen, and nasus for example. They are easy champs. In Bronze league, don't try to play complicated champs. Focus on ones that will give you and advantage. Bronze players will try to play high skilled champs that will put them at a disadvantage.

Also, don't count on others, so play offensive champions as possible. Don't go support. Play as if you're the only one that can carry your team.