Agreed with @MrsBCW , work on getting a few rainbow teams of 4* maxed, or at the mat wall, before starting on anyone else. After that, I’d suggest maxing the good 3* to help fill out your roster for war quickly and cheaply, and that’ll allow you to participate in the beginner tier of the challenge event as well. 5* are definitely closer to end-game goals, and it’ll take you a few months to get the mats to take them all to 80, so I’d hold off on leveling them until you either 1. Run out of other good heroes to work on in that color 2. Already have a few 4* leveled in that color or 3. You’re close to having all of the necessary mats to take them to 80 or 4. They’re already at 4T (I see two are so you might as well finish).
As for leveling, I’d stick to leveling one hero in each color at a time until they’re either maxed, or at the mat wall. Do on-color feedings for the extra exp and to increase the chance at raising SS. Spreading feeders around to too many mouths can slow your progress down significantly, so I would focus on the most important hero of each color at a time. Also, I wouldn’t ascend someone unless you plan on finishing them off, to max on that level, at that time. You never know if you’ll need those mats, and if you aren’t going to max them, those stats don’t increase as much as they could- therefore the hero isn’t at it’s full potential. I would also save Trainer Heroes and 3*+ feeders til the last few levels of 4* or 5* on 4T, or at least wait til a hero has a maxed out skill.
Another thing, I’d recommend keeping at least one copy of all of the good 3* (dupes of the good ones if you’ll eventually want to compete in beginner and need a full mono team). I’d keep at least one copy of every 4* and 5* you get, and one to two dupes of the amazing ones. No need for more than three though; you’ll probably never level that many with the amount of heroes you already have to level.
Honestly, I only keep dupes of the limited time heroes [that are good], because I do enough pulls to keep a dupe of a season one hero when I’m ready to level them. Right now, I have too many heroes, and not enough space, to keep dupes of good season one heroes. Up to you on how you want to go about that; it depends on how many pulls you’ll be doing, and how many TC’s you’ll eventually be running.
I’d highly recommend spending gems to increase your hero space though. Better to spend a few gems (that’s less than a summons), than eat away a hero you may later come to regret. You’ll get some space from leveling up, but purchasing the extra space will add onto that. I can currently hold 165 and even that’s not enough (I like 50 slots open for TH and on-color feedings), so you’ll have to decide for yourself how much space you’ll need, in order to keep every unique, and/or good hero you pull.
Now, for leveling (4* First, 3* Second, 5* Last):
Red: Finish BT to 70- amazing buff and heal. After that, I’d get working on Wilbur immediately, he’ll help you just about everywhere, but especially the places where it counts (Titans, events and quests); even though you have others closer to max, he’s too important to not get in the works ASAP. Afterward, you might as well take Kelile to 70 since she’s already at 4T (even though I’d usually save her til last, her fast mana hit could still be a benefit once she’s maxed). Guardian Falcon will help you for green Titans and tanks, so I’d make him a priority after. Then, I’d go back to Colen since he’s already 3T, even though he’ll only be used defensively, wars, and maybe in a red stack, but I’d only take him to 60. Then, Gormek should come next; always nice to have defense down heroes for war. Scarlett for that super high attack stat, then Lancelot for another high attack stat and buff. Sumitomo last- him and Colen are the two I wouldn’t spend mats on (that haven’t already gotten mats) unless you find yourself overflowing in blades later on. (4*)
Namahage, Hawkmoon, Azar, Rudolph (Nashgar) (3*)
Zimkitha is nice for that fast cleanse and buff, Mitsuko is very unique and could make an excellent defensive hero and Elena has an incredibly high attack stat. All three deserve to go to 70 when it’s time, although I’d be choosing between Zim and Mitsy for final ascension. Depends on your priorities; Zim for the utility, or Mitsuko mostly for fun, but also defense and offensive raiding. (5*)
Blue: Kiril is maxed, that’s good, he’s amazing for Titans with the heal and dragon banner. Next, I’d get Grimm to 70 for the best pulverizer. After that, Triton for a fast blue sniper with a healing buff. Sonya for the fast dispel. Agwe, Boril and Valeria last. Honestly, I wouldn’t take any of them to 70, so I’d move onto 3* after Sonya (4*).
Valen, Gunnar, Gato and Ulmer (Karil if you eventually want to run a mono blue 3* team) (3*).
King Arthur is amazing for red Titans; definitely a lucky pull, and I’d think he’d be the most deserving of those mats. Misandra is also good, for the fast hit and mana gains; she’ll be nice for raids mostly. Aegir is pretty controversial, so I’d only take him to 70 unless you find use for him or love playing with him. Thorne doesn’t deserve the mats (5*).
Green: Max Hansel asap, he is the best 4* out. After that, you could do Kashhrek for a solid 4* tank (okay for platinum, but no higher than that), although, if you don’t value defense much at all, and don’t need anymore healers for war, I’d move him to the back of the line. Caedmon next for the fast dispel. Melendor for the deep heal and dispel (always need healers for war). Gadeirus for the buff in green and heal. Little John for that high attack stat. Gobbler only if you struggle with minions, or else leave him, Skittles and possibly Kash til last, and do 3* next instead (4*).
Mnesseus, Belith, Brienne and Berden (keep a dupe of Berden or Mnesseus if you eventually want a green mono 3* team) (3*).
Yellow: Joon is already at 4T, so might as well max him to 80 first. Inari can be worked on after the 4* and 3* (5*).
I don’t see Wu Kong, but if you happen to pull him, move him to the front of the line for Titans and events. Finish Gretel for the mana control, then Li Xiu for the mana cut on all. Chao after for a faster mana cut on one. Danza is decent if you can handle the unpredictability, so worth considering after Chao (4*).
Bane (two if you want a yellow mono 3* team), Melia, Kailani and Gan Ju (3*).
Purple: Since Khiona is already at 4T, you might as well finish her to 80 too for that buff. Quintus can wait to go to 70. I’d personally do Obakan before Quintus, but Quintus is further. Both idk if I’d take either to 80, but if I did, Obakan would be the one I’d choose. Both Quintus and Obakan shouldn’t be leveled anymore until you at least get a few more purple 4* maxed (5*).
Max Rigard for that cleanse and deep heal, then finish Tiburtus for the last pulverizer (nice to have them in every color). Sabina for the deep heal and dispel. Cyprian last, do 3* first (4*).
Balthazar (x2 if you want a purple mono 3* team), Tyrum, Chochin, Gill-Ra (3*).
Hope this helps. Feel free to ask any questions you may have. Might have repeated a few things said already, but this is how I’d go about it. Good luck 
thank you!!!