There are five leagues in the Arena: Bronze, Silver, Gold, Diamond and Champion. Higher leagues have greater rewards!
To move up in the league, you must be among the top three rankings in the league for the week. The next week you will then be moved up to the next league. If you place in one of the bottom rankings in the league, you will be demoted to a lower league. The main Arena screen displays your ranking in the league and which rankings will be demoted and promoted.