Players are awarded a small number of crystals every time they earn a level, and also receive ten crystals every time they earn a gold trophy for an Achievement. A player's monsters may also randomly give out a crystal while the player is at their own ranch. However, once you reached level 60, which is the highest level the player can reach, then crystals are hard to get. Since monsters only give crystals one at the time.The easiest way to collect crystals is by purchasing them with real money. By clicking on the plus sign next to your currency display on your home screen, you are taken to a screen where you can purchase Crystal, Gold, and Friend Stones from your device. On this screen, you can also find a link to a page where you can watch videos and sign up for third party services in exchange for crystals in varying increments.