Kingdom Hearts II Help with getting orichilcum+, and twilight gems/crystals/stones?

i have 4 but i need 13 to synthesize ultima weapon.i also need to find twilight materials

 

In the game they only allow you seven plus's. Once you get them, obtain the rest of your items (FYI, try The World That Never Was for any and all twilight items.), once you have all seven plus's and the rest of the synthesis items for the keyblade, go to make it and use an energy gem/crystal, to lessen the cost down to seven, (This ensures that you only make one, as getting more oricalchum + is now impossible once you have them all). Congrats, you now have your one and only Ultima Weapon.

Hope this helps.

I also forgot to mention, for the twilight gems, stones, and crystals, use lucky lucky on all of your characters, along with all of their lucky lucky weapons and the lucky ring. This increases your chances of getting crystals and key items by 80%!