>>9928490If you're trying to make the details pop (so stuff like the rolls and wrinkles), I think you'd do well with picrel. Medium gray is dark enough to where it will seep into the details, but not too dark that it starts to make Moon Knight look like Charcoal Knight.
If you find that medium is too light for your needs, then I'd go darker. Just remember to experiment with your washes over paper and plastic spoons to get a rough idea of how it's gonna look on a Marvel Legend.
Also, you don't have to buy Tamiya, the picrel is an acrylic so if you prefer Vallejo, AK, any other brand, make sure to get the correct shade.