Actually, this is only KHII. You didn't have the ability to cut material costs in KH. Anyway, there are only seven Orichalcum+ materials in the game. You need all seven, and you need an Energy Crystal. You must get your Moogle to at least level 2 so that you can use the Energy items. Using an Energy Crystal will cut the required number of Orichalcum+'s from 13 to 7, letting you make an Ultima Weapon keyblade.