Its very good decision to make first team by 4*. 5* heroes needs much more time and mats.
Max Boldtusk first and Wilbur after him. This 2 guys are awesome in red stack.
+Wilbur is awesome on titans
Mel is very good hero, max him definetly. Gadeirus is only green attack buffer in game (and Brienne ofc but she is only 3*), max him second or Caedmon/Hansel if you will lucky.
Take Isarnia to 2^60. Do you have a blue 4*? If not max Gato befire you ascend Isarnia higher. He is strong 3* and you can max him fast.
Take Tibs to 3^60 and then start maximg Proteus. He is a beast, this guy will change your game and help you with beating rare quests (for mats)
Max Wukong for titans (and everything else in early game) do you have another yellow 4*? If not mac Melia.
Mel-Isarnia(4* blue maxed if you have)-Boldtusk-Tibs(Proteus after upgrades)-Wu
Best option will be max first 3* rainbow team (with healer) for rare events and raids tournaments.
Don’t worry about many healers up there, with Wukong you don’t really need offensive skills.