On the left side of the bottom row in the world map screen, you can find the “Store” icon. Tapping it will take you to the store (who would’ve thought!). In the top-left corner of the store window, you can select what you would like to buy – energy replenishing items, tools (like Jokers and Undos), or relics.
Items in the store are bought with crystals. You may receive crystals as a reward for certain in-game actions.
Gold is used to unlock locations. You receive gold for completing levels, quests, and collections.
Your current amounts of gold and crystals are displayed in the top-right corner of the world map screen.
Both gold and crystals can be purchased with real-life money. To do so, you need to press the “Bank” button in the top-right corner of the world map screen.