It varies heavily on the team used. Famine is still arguably the best defense mythic, while gard holds that spot for offense. Personally I would say famine, gard, and pharos ra are probably the best to go for overall. Infernus is all around decent but also works really nicely with elemaugrim, the dragon mythic. Honestly even the worst mythics still have some use and could be traited at your leisure. However, this all depends on how quickly you can craft them for targeting with the forge and which events come up or even a jackpot from gem or glory keys here or there.
If I were you, I would put most of my focus on Famine, Ketras, and Pharos-Ra first, the top 3 I want badly. Maybe I try to get War as well if I have the crafting materials, the rest I’ll honestly just rather wait until the next Broken Spire event for Infernus or the next Ghulvania event for Draakulis.
Interesting to see that Ketras is actually useful now. I don’t have him and didn’t think I was missing much.
Infernus is my top offensive mythic. Sometimes Gard’s as well depending on my mood. Elemaugrim (always with Infernus) is a nice backup.
Pharos-Ra, my first mythic, allowed me to 7 star all my kingdoms and although I rarely use him now, he has already done his job.
I have recently just crafted Famine and he is just perfect for those Guild Wars battles where controlling the enemy is key.
So depending on your needs, these 5 are my top mythics.