Trying to get 15000 is easy I got 21761 points, what U gotta do is in the begin first matches use STich over and over again until U don't have anything in ur drive meter anymore....then just attack and kill all the enemies and when U get to 11-20 use Stich and use him to he is summoned away, then use Genie Final Form to defeat the others without getting injured at all, then from there 21-30 use limit moves to defeat the others quickly...31-40 use Final Form to defeat the enemies fast, 41-50 just use regular attacks and Magnaga to trap multiple enemies up at once and kill them quickely....for 47 seed use Trinity limit move on those spinning heartless and although they may get there health revived all they do is jump the rest of the match instead of spin....49 seed just use glide and thunraga them, if there is an opening attack them with a combo but then run and glide fast, stay moving cause leon will try and fire a fire blast at U..jsut keep it up stay away from them using Thundaraga to defeat them.....and jumping in the middle of them and using reflect also damages them big-time....and the 50th match is just to easy...its Hades for god sake....U should get way more than 15000 points......
and to answer ur question the cup is easy, just make sure U have the Ultima Weapon