Bera 100 percent first. She is a great tank, and riduclously useful on offense.
Dr. Moreau is great as his stats are totally out of line with all the previous heroes, as is the case with all s4 heroes.
With the exception of some key titan heroes and war tanks, S4 heroes kind of make the rest mostly irrelevant.
Old HoTM’s, S1 and S2 heroes even with costumes are kind of wasted mats at this point.
There are a few exeptions (miki, costume kadilen, costume marjana, poseidon, maybe ariel, tarlak for the titans where miki can’t go)
But Bera is solid, she is probably who should get your next tabbards in my opinion.
Bera, Dr More, Malicna in that order. Bera is top hero in the defense setup. More for his stats and blind. Malicna if you dont have any other project at that time. The others can be fed to HA10