Agreed with what has been said already, finish the 4*s that you’re very close to getting to 4/70 anyway.
Now since you lack any 4* purple hitters, I’d do Tiburtus+costume next. He’s the most balanced of the ramming pulverizer trio, neither a squishy glass cannon (Grimm) nor a meat shield that hits like a wet noodle (Gormek), and that def down skill is just useful everywhere even well into mid-platinum.
Plus if you max out his costume, that 5/5/10/5 stat bonus is equivalent to about +9 talent, saving you many emblems. Additionally, if you can get a lv5 purple mana troop, he will now charge in 9 tiles flat, making him effectively fast due to the match-3 nature of this game. His costume is also awesome to have on your defense team btw.
After that I’d work on Buddy, because he is IMO one of the best (if not the best) 4* green tank. Even on offense, that atk+def down skill and the minions he provides can really improve your team’s durability. I’d bench Kashhrek for now since he’s good for one thing and one thing only: defensive tank. That’s his one role and he does it well to be fair, but he’s a one-trick pony who doesn’t do anything else.
I see you’ve started on Kiril, Mireweave, and Grimm. I’d probably prioritize Kiril at this point especially if you do Tiburtus as I mentioned. Having another healer in a different color is always useful, and the little bugger is sturdy enough that even at 3/60 you’ll get a lot of mileage out of him. Grimm I find is just a bit too squishy at 3/60, but he has awesome tile damage, and that ramming pulverizer skill is ever useful. Mireweave I’d put aside for now unless you have the feeders, she’s a bit niche and won’t really help you much outside of events where you can take your sweet time to charge her up multiple times and get her atk to something crazy like over 1000.