Queens are the currency of the game

 

Queens are the currency of the game. After each level that you beat, you will earn coins, and you can earn even more coins based on how you performed in the past level. Coins can be used to purchase new outfits, new skins, new pets, and more

There is no performance benefit to having any of these goodies, though, including the pet. If all that you are after is cosmetic enhancements, then by all means, raid the store for outfits and pets. If you don’t care about any of that, then don’t worry about buying any of it.