Do you want to have the cards for a card based minigame or just collectibles in the game?

collectibles in the game

put them as a key item, then use the built in item book plug-in. Might I suggest if your going for a collectible card route you make them perm usage in-battle items as super "summons". Then later in the game have a tavern owner give you a choice of trading them all in for a set of super weapons or if you clear out a secret dungeon give you a final awesome card.

thanks for the idea!!!