Im not too smart at this either but one of the things you sort of want to have in a team:

A tank

A tank killer

A support/healer

A main character

you can have a ninja that does both and stuff like dat, and your main character can serve as any of them or another category i cannot think of :(

Looking into each ninja's statistics you can find what they do best. (their main attributes). then you want to position your team correctly. I think the best way is to have your tank in front (to TANK the damage) then your tank killer, then your support, and finally yourself. This isnt always the case so chose what you want to do. Then you want to see what each ninja's weakness is. Most tank killers as such have to be balanced to make up for their high atk or nin, so they often have little life. some healers can heal well but either do no damage for standard attack, or very little. take these things into account and look at your teams ninja, the decide on positioning and maybe change a few ninjas around. You also might want to take into account how your team synergises/works together. this is mainly just for support characters and passive moves, like making sure the buff goes for the right ninja and the sheild goes to the person who needs it. after that, i dont really know so just go into a few fights and whatever your team gets hard countered by, try watching/ fighting again and seeing how their team is countering yours so well, then figure out why, and see if your current ninja can cover that weakness.

I dont know much more, hope this helps!

:DDDDDDDDDD

i realise its 3 years old and its unlikely youll read this ;-;