-Green: Get Little John to 3/60 (currently 2/27) or switch to Buddy? Should I bring Caedmon to final ascension when I get one more shield or should I leave him at 3/60?
-Red: Ares or Wilbur?
-Blue: Magni, Triton, Isnarnia or Kiril?
-Purple: Get G.Panther to 3/70 (currently 2/9) or work on Proteus?
-Yellow: Get Justice to 3-70 (currently 3-7) or switch to Wu Kong
You aren’t close enough to having a set of 6 color-specific epic ascension mats (e.g. darts) to be working on 5* heroes yet. 4* heroes take a lot less hams, feeder heroes and ascension mats and often add nearly as much (or more in some cases) to the overall team.
In your specific case:
Green finish Caedmon, a solid workhorse hero. Buddy follows, but his very low attack stat means he should be paired with a solid attacker (like Caedmon)
Blue Grimm is a superb start. Kiril should be you next priority. He may seem unimpressive but he’s one of the best 4*. Useful forever.
Red Wilbur without a doubt. He’s amazing. Bring him against every Titan. You also don’t have the mats to get Ares to fourth ascension, and he’s not very helpful until then.
Yellow Switch to Wu. Combine him with Wilbur against titans and all your allies will gawk at you in awe. And you’ll get more ascension mats from your high performance.
Purple okay, this one is the hardest. I’m going to go with Proteus. Panther works best paired with another strong purple attacker, which you don’t have. Proteus is amazing as a stand-alone hero.