You should have the cash to do this after a couple of resets, if not before.
Stick with the first deck - the cheapest one. As you click on the treasure chest to collect cards, the 24 slots at the bottom of the screen will fill up. When you've gotten all 24, you'll have to spend a crystal to continue with that deck.
Simply click on the chest, then select a card from the deck below to upgrade it from bronze to silver (I recommend the Lizard Den for a healthy gold boost).
That card will bow upgrade, and your deck will clear ready to be collected again.