IMO since you are F2P, I would definitely focus on expanding your 4* bench rather than your 5*. The ascension mats needed for 5* take a long time to save up for and you can lose a lot of efficiency rather than having a robust 4* bench that will increase your odds at getting those ascension mats.
More specifically, I would prioritize maxing all those 3/60 4* first, and then begin with the 0 level 4*s. All of them are highly useful in all aspects of the game. I think you’ll find the game more enjoyable once you have options to add depth to your gameplay.
On a side note, out of your 5*s Delilah, Misandra, and Sartana are top notch. The others I wouldn’t go as far as 3.70 until you have enough mats and no other options.
Finish Rigard, Kiril and Grimm. Those 3 are instrumental in beating players in raids and wars and setting good defenses for the same content.
Try Wu, Kiril, Grimm, LJ and Melendor for attack. You’ll be able to beat nearly any team with that tile damage combo. Kiril dragon banner + Wu cascading tiles into defense down heroes from Grimm is divine. Adding the Green stack will give you high tile damage in Melendor, a debuff and mana suppression from LJ.