It's hard to believe that there were that many people out there who were letting the former 99¢ price tag of the fantastic NimbleQuest [Free] put them off from downloading the game, but, hey, these are weird times we live in. We've got a review up if you need some additional convincing, but hopefully the $0 price tag is all you need to download this super fun game.
Once you do, I recommend picking up the $3.99 red gem unlock IAP, which is basically the Nimble Quest equivalent of a coin doubler. It goes a long way in speed up your overall progress, as all your upgrades are paid for in gems, and the more gems you can earn, the better. Of course, red gems are totally optional, it's just going to take you a little longer to unlock everything in game.
Also of note is the fact that Nimble Quest was just updated with iOS 7 controller support. Of course, actual controllers are nowhere to be found yet, but it's cool to know that there's yet another game out there that supports 'em when they get here.