Which 6* to rank up?

Pizzavelli

I can’t decide on which one of my 6*s to rank up. Any advice is very welcome:

Black Widow (DO) (unawakened) to R3
Hercules (unwakened) to R2
Tigra (unawakened) to R2
Domino (unawakened) to R2
Immortal Hulk (unawakened) to R2
Ghost (unawakened) to R2

Pizzavelli

Might be easier to show my current top champs too (attached)