Worked at Lv64 with 12721 power with following lineup:
x Naruto*3 Main
Kankuro*3 Neji*2 x
x x x

Skills: 3-1-3-3-3-1
Summon: Chameleon

Use Neji's Mystery at first round, then just watch Jiraya dying.
On first round versus Gamabunta use Naruto's and Kankuro's Mystery, and Main's Mystery.
On second round - use Neji's, Naruto's and Kankuro's Mystery.

Gamabunta fight always random, so might take few tries if it kills any character, instead of Naruto clones.