In the Mushroom Cup use the following

Any character will do

In the Flower Cup use the following

DK,yoshi,Peach,luigi,Toad

In the Star Cup use the following

DK,Peach,Bowser,Wario,Yoshi

In the Special Cup use the following

DK,Peach,Bowser,

Over all i would use Bowser or DK(Donkey Kong).