Yep, definitely needs improvement on lighting and value. It took me quite a while to figure out what's going on with her 2 hands, cause everything, including the gun and what I believe is a sword, is the same shade of black.
Well, to start with, that composition is fairly bad. Her pose and the angle made the cluster at the top right of her head very hard to read. I can somewhat see her fingers, a gun, a sword-like thing, and some robotic thing on her suit.
When drawing and designing, it's important to make the silhouette readable. When you desaturate the image (meaning putting it in black and white), that top-right cluster becomes a total "WTF!?" area.
Also, here's a paintover demonstrating light source. It's a 2 minutes scribble, so it's not perfect. I put a strong lightsource on the top right to generate high contrast, and also a weak lightsource to our right to create a very dim lighting effect which makes the silhouette readable. I also erased the character's left arm's ornament-thing cuz I have no idea what it is. To fully fix the value structure of this artwork though, the only way is to redo the pose. I can't really find a way to totally separate those 2 hands and the sword.
There's no sword actually. the ornament is actually the part of barrel of the second gun she's grasping that you're calling sword. I need to improve my shading amirite? So the main objective is to define the lightsource better and making the silhouette readable! If I'm wrong, you can correct me. I am really in debt with you. Thanks for the feedback! I really needed it badly! Any more advice will be appreciated deeply!
Well... that certainly is a confusing gun design xD
And yeah, just try to define a lightsource then get shadows and highlights right. Also, if you ever decide to draw that character again, the orange glows on her suit creates tons of other minor lightsources, which is a pain in the arse to draw.
If you want quick lighting practice, just draw a sphere in extreme lighting conditions. Like this [link] I do recommend getting a real life sphere though. Put it under 1 or 2 lamps, like desklamps, and see how it works.
You need to think about where your light is coming from, and have some higher contrast between your light/shadow.
If her outfit is supposed to look black, there needs to be black areas on it, if you want it to look shiny black, mostly black, with some grey areas that are where the light hits, and some white reflections of light. You can also use a light blue, instead of grey to represent the areas that are lighter on a black outfit, blue works better for a flat black, rather than a shiny IME.