Don't want to spend money in this game? The best way for you to earn higher tier cards is through login bonus so make sure you log in the game every single day.

Focus upgrading your main cards or those who have higher rarity. Those with low rarity will be kicked out of your deck once you collect new and better one.

Always check your collection tab to see how far you are from completing all cards as well as for you to collect rewards from completing your collection.