Well the first thing you need to do, is that if you can't beat the first form of Marluxia, then like the first post said, to have 15-20 cards in your deck, so you can reload faster. Have Card ranges from 0,8,9, so then you can have a lot of card breaks. An important item you should also have, is to have the summon Tinkerbell, and have Card range 8 for cure cards. Supposidly, if you just combine, to make combos, then you would beat his first form. Oh and about the combos, you need to look for the combo that does the most damage. So then you can stock up on those cards.
After you beat his first form, then your going to fight the second form of Marluxia. You he's going to start moving on his flying ship or something, but now he's harder. You neeed to have a lot of cures, and again Tinkerbell. You also need to have at least 6 Cloud cards, so then you can do twice Omni Slash on him, which would take away a lot on his HP coumter. So then I like you do when you were fighting his first form, you need to do combos on him. Also I'd advise you to use the new keyblades, called One Winged Angel, Diamond Dust, and Ultima weapon, because they are the strongest types of keyblades on the game. If you have those card, then your ready to beat the game. Hopefully, you'll beat the game with these strategy. If it doesn't work, then with this strategy, you can now find his weakness. Remember, sometimes the strategy of other people doesn't work on others, because some times they do stuff that are way different, so just try it out. Well thats all I can say about beating Marluxia, and I hope you beat the game.
Dark32