Power-ups
Instead of purchasing power-ups, try to save them until you are past level 15. During the tutorial, when you are forced to select the power-up, tap it again to deselect it. You will keep it and have it available for later use.
Restore lives
Advance the time on your device by 90 minutes to restore all three of your lives. Afterwards, set the time back to its correct value. Free bonusb Connect with Facebook to earn a free life, coins, or another bonus. This will also allow you to transfer lives from your friends.