Magic is not as complicated as people think... Ok the if not the poker idea, how about this:
Kill a monster, get a change of recieving that monster\'s card (if a card spell was cast before the monster died). Those cards have a certain HP and Attack.
Out of the cards you have, you choose 15. The comp shuffles. Then, both players flip over the top card and the 2 monsters battle. Each monster victory will be counted. The person with the most monster battle wins on their counter, wins the game.