The planes of forms here are really confusing. Maybe thats part of your style, I don't know. But its kind of disrupting the shape of the helmet here for example.
You'll want to get rid of this brightest highlight on the skirt(?), it's trying to turn the cloth into plastic stuff. Save that highlight for the metal, kick it up into white even. If it's kind of shiny, maybe your intention, contrast up to 11 is the key. See second half of
this post. If the shininess is WAY out there, like chrome, adding a light cooler version of the color you have around the edges sells this effect even more. Basically that represents a sky reflection (but it's less compatible with dark BGs.)
You have to know I think, exactly what the properties are of what you want to draw/remake before you remake it, including how light bounces off of it. Use a crapload of reference if you can, then let the games begin.
The right forearm blends into the cloth. IMO you could cheat, and drop some dark shadow on here.
That's one specific area. I'm seeing at least 4 areas that just meld into eachother value-wise so you need to separate it with lines, plane changes or straight up blobs of shadows.
The feet are pretty malformed. I'm guessing you have these problems with ambiguous forms overall, you're thinking too much in 2D and not enough in 3D. You've winged great looking stuff in 2D design terms, but this may be at the root of the two big problems, the wobbly edge highlighted shading, and sort of unbalanced form.
......1X artifact on upper left background, on 4X upscaled picture