You can unlock every level in the game for free, without spending any money. Levels are unlocked one world at a time, so all that you have to do to unlock a world is to beat the world before it (AKA the world that you are currently playing). Repeat the process until you unlock every world. It takes time but not money.
Some characters can be unlocked for free. For example, Lep’s friend Finn can be unlocked by liking the game on Facebook, watching a video and earning a certain number of gold pots.
Bonus worlds can be unlocked by collecting pots of gold and keys. If you go to the world select screen, scroll past all of the regular worlds to find bonus levels. The first ten can be unlocked with pots of gold, while the next eight can be unlocked with keys. The last two are available right from the beginning as time attack stages.
Power ups include the helmet that gives you one extra hit point, super speed and super jump boots and Super Lep. Get five doves in a stage to get Super Lep, and hit the clover blocks to find the others. Also, check the App Store often and see what bonuses have been temporarily freed up upon download. If there is a new freebie available, delete the game and then download it again, if you don’t mind losing your saved game.
If you want to get rid of the annoying advertisements in the game, then make a purchase – any purchase – from the IAP store. Pick the cheapest one that you can because no matter which one you make, the ads will instantly go away. Or just buy the paid version of the game from the App Store, which should only cost around 99 cents.