All items on your deck automatically earn money, so the more valuable the item is, the more money you will make. And this money will enable you to buy more valuable jewels instead of putting hard merging work into creating them. This means you don’t have to start by merging the least valuable metals and save a few steps on the way.
Every 10 seconds a new jewel will appear on your deck, as long as there is space for them. However you can speed up the process by tapping on the respective icon on the right. While you merge jewels and earn more money you will also upgrade your deck and receive more space to place your jewels.
Basically all you do is tap or click on the screen, merge jewels, earn currency, tap some more, merge bigger jewels, get more money, tap even harder, merge the biggest diamonds you have ever seen and earn the sweet reward of even more money! It’s a never ending spiral of tap and reward, and it is ultimately satisfying.