Red beats green, green beats blue, blue beats red, and yellow and purple beat each other.
Organize your team around what you find in the world that you’re presently in. If you are in a green level, such as The Sore Shores III, then load up on red teammates.
If you can’t beat a particular level, go back to old levels and beat them over again, so that you can earn more cards to use for evolution and for gaining experience points.
If you’re looking for the right materials to evolve a max level card, first, go to the max level card’s profile and it will show you what you need to get.
Any card that you can’t add to your main battle party is either a level up unit or an evolution unit. Tap on their profile in order to figure out which one they are before you sell them or use them for anything.