Any level can be completed without purchasing hearts, coins or boosters, but if you're still not able to beat a level or are getting frustrated, consider the purchase of a booster. Boosters can give you the extra edge you need to finish a level so that you can get to all the levels we've released recently. There's nothing better than playing new content!
A good trick is to make as many supers as you can! They can be created by combining one or more power up.