I suggest bringing a ninja who sets up a class specific barrier that provides buffs to your team

barrier ninjas to bring for each class:
lightning - 3 star sasuke
fire - anko
water - haku
earth - yamato

summoning - tonton

other good ninjas with buffs to bring are:
asuma (wind blade) - has a passive buff of increasing the attack and ninjutsu of your team
guy - increases the attack of your team

also always bring enhancement for your second passive for kyuubi

you'll be able to unlock summoning at lvl 50
and tonton has a damage bonus for bosses
it does more damage than any other type of summons
it's the only one we use for kyuubi despite your level or how many other golden summons you have
tonton's the way to go for this