mmmm keep the high level at the back, because you can use their attack anyturn, but yeah, when you get full party, i prefer KOS-MOS,Haken(he is a must, you will see why), Archen and Xiaomu, in the front, others in the back,

Kaguya and zebra, Xiaomu and suzuka support movie are the best( easy to chain into any combo, kaguya and is a little bit easy to get forced evasion though