All our levels can be completed without purchasing lives, coins or boosters. Our developers only release levels after they personally ensure that levels are beatable without the use of purchases. Boosters and coins can give you the extra edge you need to finish a level, but they are entirely optional and are not needed in order to pass any of our levels.
Try and combine lanterns to clear harder levels - each lantern combination gives you a different effect!
If you're still having difficulties, visit Youtube.com and look up a walk through for the level you're on! Other players may have found strategies you haven't seen before!