So in addition to trying to build a good poker hand, you're trying to build a hand in the suit that benefits you most depending on your current monster situation. These effects are boosted by how good your poker hand is when you've reached the showdown at the end of your turn.
(Or if you've put together a good hand you can end your turn early.) Each suit also does something specific: clubs deal damage to all enemies, diamonds do damage to the enemy with the lowest HP, spades give you block, and hearts (cleverly) heal your own HP. Your poker cards each cost one energy, and you can discard them in exchange for a new one from your draw pile until you're out of energy.
