Forum:Fusing/Evolving Tips/Help

Hey I am looking to better my squad but im not sure who to focus on lvling and evolving.

My squad consists of Thunder Eze Max lvl (leader)- Tinkerer Elulu lvl 30- Leviathan lvl 26- Rage Beast Zegar lvl 28- and another Rage Beast Zegar lvl 15. Is there anyone who i should really focus on lvling and evolving in my squad? Is there any that i should  least focus on? Also I have been saving up gems and am able to hit the rare summon twice so is there anyone that i might get in there that would benefit my squad ??? Any suggestions or input would be greatly appreciated, thanks.