When you first get to Traverse Town, you will probably be about level 7 to 10. When you get on the Gummi Ship, go to the Coliseum and get to fight in the Tournament. Get as far as you can. Most likely you will lose to the enemies just before Cloud. If you lose to Cloud, reset the game and try again. After you lose to the enemies just before Cloud, go on your Gummi Ship. Go the opposite of Traverse Town to the Deep Jungle. When you leave left there, you will also get the Jungleking, a new Keyblade. Return to the Coliseum and you will now definitely be strong enough to defeat Cloud. Enter the customize menu and set everything constantly on Goofy and Donald except HP and MP recovery items. Put those on only in emergencies. Then, equip Goofy with Hi and Regular Potions and two Ethers, Donalds with regular Potions, and Sora with one Hi-Potion and the rest Mega Potions. You should now be able to defeat Cloud. If you want to be stronger, complete the Alice In Wonderland section after Deep Jungle. You should be strong enough for Cloud or Cerebus.