This trick is very useful;
When you open a new chest, check out how many stars the last card got. If it got 4-5 stars buy a magical chest. If it got 3 stars buy a golden chest. If it only got 1 or 2 stars you should buy a wooden chest.
If you do it with this method the chance you will get new cards is much higher. Sometimes people are spending so many coins and buy so many chests, but they keep getting the same cards. If you don’t find any new cards it is highly recommended to move right into the next level.
Before you move into the next level you should make sure you didn’t miss any rare card.
On here you will find the full card list.