Would definately go with Kimimaro.
Talents 3-2-3-1-2
Gamaken as a Summon

AO - Kimi - X
Main - Chojuro - X
X - X - X

Yeah he is a must... The difference between a gold summon and a purple summon is a 4-combo and a 7-combo... :D

You can Swap water enchantment for neurotoxin btw, if you think you need more control than damage. But I would personally beef up chojuro and f**k them up :)

Hope you get your Gama (or Mei)!