Coins
Open for Dragon Coins, which are used to grow dragons! Dragon Coins can be found in Inventory / Crafting (the third side-tab) / Red Coin icon (the middle icon at the bottom).
Lesser Dragon Caches come from hourly challenges, while Greater Dragon Caches come from events and the Store. Greater Dragon Caches can also contain tradable Golden Dragon eggs, which can hatch into a full-fledged Dragon immediately!