If you have Kage treasure unlocked. Then I would draw from it, and go for Mei and Mabui. You can make a really good team with those two.There also also good ninja with Danzo and Mifune, Then you could build the Linghting Blitz team of Kimi,Mifune,Danrzo, and Lightning Main.

Water Main you want to try for Mei and Mabui, or if you can get Mabui then with Water main you can go the Chaso shark team.

Overall kinda need you ninjas to know what you can build team wise.