I think there should be the 3 tailed Beast (I turtle like sea creature) as a mount, it would be a little more powerful thank shukaku.
Turns: (not sure now many turns shukakau has but 5-10 more rounds than him)
Discription: A force to be feared. A swing from its tails or claws will be the end of you, but its true power is still unknown, buy with caution
Cost: 145 gems or higher
gold: 12000 gold
attacks 3 times a turn, each doing 5-10 at low lvls and 10- 20 at higher lvls
Doubles defense, attack increase (depends on lvl) up to 30 attack
Turns: gives you 6 more turns
travels: get 5 extra travels
Neji would probably chose exactly how much power it does but thats my idea