I have Joon at 4/30 and just got Onatel, yay!. Should I continue to build Joon to max him at 4/80, or, start on Onatel and get her through her humble beginnings first?
I would finish Joon since hes pretty close to being maxed then work on Onatel
You have spent the 4* ascension materials, you absolutely, definitely should finish Joon.
There is a lot of competition for Monk Emblems, but a Joon 5*+1 would have a 6% chance to resist status ailments, a handy additional ability even if you leave it at 6%.
Wizard Onatel is not quite as useful, thought the improved stats for both Joon and Onatel, as they level up in their classes, are useful.
I might feed 2* and trainer heroes to Joon and 1* to Onatel. That strategy will conserve food (if that’s a problem for you).