Gems are a currency in that you can earn or buy to spend in game. You will see how many Gems you currently have in the upper right of your screen while you are in town. To obtain more Gems simply click the plus sign next to your current Gem number and a store window will open with different options to purchase gems. Once purchased, the Gems will be added to your current Gem count.

You can also obtain Gems via quests and other means. From within the store window you will see options such as “Watch A Video” or “Get More Free” where you can earn free gems.