Spending Gold in Clash Mini
The shop has several items that refresh regularly that you can spend your gold on. These items are unit copies of either Heroes or Minis. It's best to spend coins on whatever units you play with, or want to play with, the most. For example, if you really want Countess to be your main Hero that you use, you'll want to spend coins in the shop on Countess every time you get the chance to unlock and then level her up. This will help make her more powerful.