I would suggest to have a look at this valuable thread:
not necessary due to the emblems, but the thread lists the best heros for each class. Focus on levelling these heros first, if you have them.
Other than that, I try to keep at least one copy of every 4*, some dupes where i personally find the heros good enough. 3* Star I keep only the best ones.
I have a roster space of 127, so nothing wrong there.
I haver never purchased any additional teams, 5 is enough.