Gems are used to activate the machines and collect cards to complete your Album. You can also use your cards to obtain extra lives, coins or more gems based on the value of the card. This is done by adding three of them on the Free Prizes Dashboard. To collect cards, tap “Get more cards” on the main screen of the game and go to the Machine Room. Use your gems by simply tapping the Push button on the machine. You can also take 9 cards at a time by tapping the Push x 9 button.