To make more gold, hit the missions area to take a look at exactly what you need to do to complete all your missions, then commenced finishing them one by one. Gather your rewards and watch the gold accumulate and build up, then when you have enough, go to the store in the game, and purchase several new decks of cards. One deck expenses 200 coins; the multi-deck packs can be acquired in the IAP shop using real-life cash.