There are two types of currency in this game, they are Gold and Mystical Orbs and each has multiple uses.
Gold
Although you can spend gold on unlocking new areas early it is more beneficial to save it for the top-tier costumes as these locked areas will become unlocked naturally through Gameplay anyway.
Extra Coins
If you are running low on gold you can always trade in 10 Mystical Orbs for 7,500 gold by selecting the 'Store' tab on the 'Main' menu.
Sully
When you're not playing, you can let Sully send notifications when he has more loot to unlock.