i believe the best way to get power right now i think is ninja assist and myobuku so focus on them but as the one above me said get ur runes to at least level 6/7 for decent secondary stats and stop myobuku at map 8 or 9 , focus your refines on position one as that will slot will hold your most powerful ninjas when you recruit them . also while spending coupons make sure that you don't get only the fragments of the ninjas you want . ensure that u also get some power up items like runes , myobuku or training portions . also do not spend coupons on kushina i completely recruited her for free slowly over time . aim for kakuzu earth grudge fear 4 star , minato edo tensei 4 star , naruto sosp or sasuke rs 4 star as he is about to get decent BT.

as for the team i think the one you are using right now is the best .