Ranking a 5* to R5

Mentalboy1

Hi I now have enough resources to rank a 5* to R5. I'm not sure if should do this or rank 4 my 5* Dr Doom? I can't do both. My options are if do not go with doom:

Cosmic ghost rider duped
He is great but tricky to play

Black widow deadly origin
I love playing her her dot is helpful

Hulkbuster
Great to just go all out with

Iceman
Good and nice immunity to bleed

Tigra
Again good but tricky to play

Domino
Love playing her and have a rank 3 5* massacre for her synergy

I would have put a poll but it won't let me.

Thank you.

Yodabolt21

Doom for sure. But CGR isn't tricky to play.

Rahultripathi

First comes doom than comes the rest

Scrubhan

Best to get a rank 5 quickly and cgr can get through a lot of content. Rank 4 doom later.