Wow. You’re much luckier than I on the troops… (Only have one 4-star.)
That said, I think you need to be concentrating on getting a group of four-star heroes maxed. At the very least, you need to get a rainbow team up to 4/70. Frida at 3/70 will probably “work” here. Ultimately, the four-stars are going to be the backbone of your team for the forseeable future. (I would wait on taking Frida to 4th tier until you have a couple of 4-star blues maxed, personally.) I’d use free gems and TC20 to get those four-stars.
Good heroes to max:
Balthazar
Muggy
Tyrum
Gato
Gill-Ra
Berden
Ulmer
Don’t bother feeding:
Isshtak
Prisca
Renfield
Oberon
Friar Tuck probably not worth it, as you have Belith, who is better.
Valen and Gato charge at the same time because they’re the same color and speed. You can deal a very powerful 1-2 punch to one enemy by using Valen to drop defense → Gato to kill or heavily injure a single target. So I’d level up 1 Gato 
I copy from your 1st post which is you can not create new thread yet.
IMO, priority left to right project leveling heroes.
Red: -
Blue: Finish Frida, and start Gato, but you already start Karil, so finish Karil. After Gato, next Ulmer. Greymane after there are no other blue.
Green: Finish Ishtak, Muggy, Berden
Yellow: -
Purple: Gill-Ra, Tyrum, Oberon, (Renfeld and Prisca only if you do not have other purple)
source:
Berden needs to be a priority over Ish.
In my honest opinion, I would focus on developing at least 2 to 3 maxed 3* teams. Then start levelling 4* prior to five star.
For your 3* focus on
Blue - Gato
Purple - Balthazar and Gill-Ra
Green -