Tap the "Roulette" button at the main menu to win various prizes. This can be done for free once per day. You can also earn a free spin by leveling a certain number of times. Earn achievements to claim various rewards. Sign in daily to earn gold and occasionally diamonds. Online rewards can be claimed just for remaining logged in the game. They are indicated by a present icon on the right side. They usually reward you with gold and can be collected every few minutes.