Easy money
Disable the auto-shutoff settings of your device. You can make money continuously if the screen does not go to sleep. Take advantage the free offers in the lightning-bolt icon. This can give you boosts in different rates and is more effective at later stages when you need to have higher earning power and waiting times. Connect the game with your Facebook account to earn the multiplier options in game. You can also invite friends to earn free offers for the Billionaire level.