I am glad to see you trying to improve. I will offer what advice I can in animated gif form:
1. Your palette is very light and very low contrast. See how when zoomed out you can not distinguish the outline colour from the shadow colour? This indicates that your colours don't have enough range. I made the darkest colour darker, and replaced the white of the eye with the same light yellow colour as your highlights because they were so close together: another dark colour is far more useful and now you have more flexibility without adding any colours to the palette.
2.So this is crudely done, but basically I just made all the edges deeper, and don't be afraid to be bolder with your shading. I also aliased everything, and a mess of other stuff but basically this: try to make the details more distinct using areas of contrasting dark and light colours. I assumed that lightish area was teeth, for whatever reason. I really can't even guess, I get to this later on...
3. It also helps to think of these in terms of these solid geometric shapes when it comes to lighting. You have that a little, I can see how you have considered the shape of the head and the eyeball but in general it still looks like non-planned "highlight = top-left, shadow=bottom-right" kind of drawing.
More generally: I know the temptation is to draw whatever you're capable of when you're learning, but amorphous blobs and boxes, while they may give you the nice psychological lift of "art completed!" they don't make for very empathetic characters, and they don't make for very good practice either. Even in pixel art it helps volumes to learn from subjects grounded in reality and furthermore there isn't so much someone can tell you for critique. How am I supposed to know how your cyclops sphere is supposed to look? I recommend for your next project you do something we can really relate to: a face, something from nature, anything like that.
