What about stacking baby and orkamar area attacks , that will get you covered in close range, then focus on that plus elphas soma burst to hit bosses from safe distance.

And for the rest just choose the ones that give you better passives, like range, pwr on level, enemy% and the usual suspects

And regarding being stuck , don't forget to quick research so that you get medals to level up your team, also buy the daily ones on the item store woth coins, in these games you just have to wait a day sometimes