Who to champ next?

Eventually I want all the characters. I am a 4* transitioner but still a long way away from investing iso into the 4*s. At this point I have champed a little over half the 3*s and am primarily working on the other 3 stars. But in the background I want to build up another 2*. I already champed obw, cstorm, mnmags, ares, hawk, and wolvie. I never bothered to build up the baby 2*s (Thor, ht, etc) because I maxed their lazy counterparts long before championing. With all that being said which 2* should I build up next?

Tl;dr which 2* should I champ next? (Already finished: obw, cstorm, mnmags, ares, hawk, and wolvie)