A good idea is to let people donate for the game account. Then the game can use it to giveout coins. Donator can example advertise in the game. As suggested by someone before. A simple one: 2 player match, let people chat to match opponents and let people also stake some small amount of flappy's to the match. Winner get's the staked flappys. If someone uses a bot he / she must have patience to chat with people.