Heyo, that's because you can break through the ninjas at 4 stars specifically and you'll need 200 fragments to upgrade them to the next star level. It's much better if you break through them first, since the ninjas will be much more helpful there. Also Monkey excellent suggestions


About ranked battle teams, few ideas from my side, you could use Minato - Gaara - Kurenai and your main as number one team for example

One team you can build is some taunt or blocking tank, for example Kimimaro or Hinata GNW position ones, followed by Sakura Gnw, Tsunade, Hanzo, etc supporters that can heal for example.
A third team can be something with Pakura, Kimimaro/Hinata and two any supports, you c*e Kushina there as well.


Play around with the supporting ninjas to see which combinations you like more.

Good luck and hope that helps!

Yup