Hey there, you've done a pretty good attempt so far. One of the things to remember with doing really low res pixel character like this is that you have to rely heavily on the implications for proportions rather than trying to create them directly. This requires looking at the impression of what you've created (by zooming out and looking at your character). Changing even 1 pixel at this resolution will undoubtedly change the entire proportion or orientation of what you were working on. Here is an example I made in the past that seems close to what your style looks like:
If you notice her wrist for example is only 1 pixel wide, any wider and it would have been way too thick. Sometimes you just have to experiment with the pixels, because you can always undo and try again. As far as the coloring of the character, try to add a little more contrast overall by making your darks a little darker, and your lights a little lighter. When figuring out how to approach lighting, similar to what ZerotuL mentioned, choose your light source ahead of time in your head and then go from there. Aside from any artificial light, typically humans see the light from a top down perspective (or top left for a more dynamic look). So just imagine that the sun is above your character, and draw your shading and light with that in mind. Pay close attention to the forms of your character. Just by adding light and shadow, you can determine the shape of an object, without having to redraw the object. Above all, use reference if needed, even for something as small as this! This is pixel art, but it still needs to follow general instruction as far as proportions, lighting, and form over all. Last thing is reverse her right leg (your left), as it is more or less backwards proportionate to the rest of her pose.
Overall, I really like your choice of colors, and she has a pretty good pose overall! See if you can hit a second attempt with the above guidelines in mind, there's nothing wrong with reworking your art in an attempt to improve. Good job!
