I got a HOTM after playing for 2-3 months. I was so excited I immediately started leveling him. 3 months later I got a second and ditto. That slowed me down considerably – it took me about 9 months to finally max the first. Meanwhile, my 3* and 4* stagnated in green and purple because of that. Oddly enough, I am strongest in 4* in red, the colour it took the longest to get a 5* in.
So I always stress do not level higher star heroes until you are ready with a good set of the ones below.
I mostly agree with the others’ responses. Here are my comments:
Purple:
First priority is Rigard. He’s useful in the map, war, raids, against titans, tourneys, and events.
You’ve invested a lot in Cyprian, so he’s a distant second. He appears to be in your defense team, so level him up, too. In the mean time, cross your fingers for another four-star hero. You may be waiting on ascension materials, in which case the picture is less clear. You have a second Rigard and Sabina, both of whom are good choices. I also like Gill-Ra since she is useful in bloody battle tourneys (though, she has some haters). I’ve not used Bjorn, so not sure about him though others in this thread have; I defer to them. I will say, Oberon is your last priority.
Yellow:
First priority is Wu Kong. He’s a must for titans.
I’m not a fan of Hu Tao, due to his speed, so I have the same “cross fingers” advice for yellow. They’re both at 3.60, so you likely need ascension materials for them, too. In that case, you have no option but Kalani? Cross your fingers and your toes?
You didn’t ask about the other elements, but I’ll offer some unsolicited advice and recommend Sonya and Grimm ahead of Boril and maybe ahead of Gato despite your investment in him so far. (Others in this thread feel differently, and make good points. Gato’s special is useful and as a three-star, he’ll consume fewer materials to max. Boril’s reposte is particularly effective against teams featuring one or more hit-them-all heroes, but he’s too pasive for my taste, but that’s an opinion.)
I’d also invest in Berden and/or Mnesseus ahead of Skittleskull.
You seem to be lacking materials for Grazul, so invest in Boldtusk ahead of Kelile. Boldtusk will be useful for a long time (as will Kiril who appears to be waiting on materials, but as soon as you get them, he’s a contender as your next blue).
Good luck.
Cyprian is excellent in any PvE team, I think. So, I will max Cyprian immidiately after Rigard, if OP do not have maxed Boril.
Agree.
Do not agree for Sonya. Grimm maybe, if OP does not have a def down hero, but I will definitely max Boril, because it seems than OP have also Boldtusk, Wu Kong, Kiril and Rigard. But definitely max first Sonya, she requires some love. Costumed Sonya is good war center, I think.
3 4* healers, riposter and Wu - deadly team for all events, quests and Atlantis (to get those Proteus and Wilbur).
Most people use their world energy to “farm”. They play easier levels over and over in order to get recruits to train in your training camps and for items that you will need for crafting battle items. Once you have 3 heroes of every color, you will find that completing those levels will be much easier.
Thank you all for great replies!
I made quite a good progress on events, s2 and s3 map 
It’s time for another round of ascends. And I wonder - should I keep part of mats in hope for some lucky pulls?
My long term goal is to be able to finish legendary part of challenge events ( mats and coins 
)
I think that my priorities should be:
Blue - Grimm;
Yellow - no idea - Hu Tao is ready, but that slow skill… maybe Chao it Li Xiu?
Purple - not sure about Cyprian;
Red - Kelile or cross fingers for another one?
Green - Caedmon is almost ready, but what about LJ? I heard that he is worth embleming…
As you already have good fundation on healers, i would focus on hitters. Grimm, Kalie and Caedmon are no brainers. On yellow i much more prefer Liu xiu but Chao will be decent too. When it comes to purple, Sabina is miles ahead over Cyprian in long term usefulness, but noseless riposte could be tremendous help on epic and legendary events. As i said earlier you dont really need more healers for now. You already have a nice roster, the only thing required is time to develop it.
