Okay, I am finally ready to post a proper critique!
So first, I think it says a lot that
this piece is something you're really proud of. It shows me that you know where to start on a drawing and how to realize a figure. That you can draw the skeleton of a character without getting bogged down in the details, like many new artists are compelled to do. But I still think there are things you can improve on here, even in just your line drawing. First, I'd like to see you draw more complex, complete, and dynamic figures - like
this. Before going into anything like the face or clothing, I believe just doing some figure drawing will help you smooth out some of the inconsistencies in your anatomy. For instance, in your sketch, the back of the neck more or less vanishes into the shoulder, and the arm in relation to the chest looks off. Plus, it reads very flat. Like a two dimensional character and not something that has weight and volume to it. I think in general just going over anatomy, practicing complex poses, and familiarizing yourself with the human body will drastically improve your art. I think drawing characters of varying body type will help as well.
Second, I think a simple way for you to improve the overall look of your art is to learn more about clothing. Right now, the way you draw clothing is very flat. None of it moves with the characters, pulls or stretches, folds or creases, or anything. It all sits on the character as if you were drawing the clothes as skin. Think more about what direction the clothes are being pulled in and what gravity would do to said clothes. In the
girl jumping picture, you've got a character expressing a lot of movement, but almost nothing besides the post suggests that there's anything actually going on. Perhaps, if she's jumping, the bottom of her skirt / shirt would lift slightly, like you have the hair doing a little. They would fold along the middle to conform to what the body is doing, and stretch along the back and chest where it would be pulled tightest. Practicing things like
this will add action and make the scene more believable.
Third, shading, shading, shading. I can see where you've tried to add depth, but it's all extremely uniform. Not all shadows will be cast in the same darkness. Try working more gradients into your shadows, where the shading furthest from the light source is darker than the shading closer to the light source. Does that make sense? This also applies to highlighting, which I see very little of in your art. Areas more exposed to the light source would be, understandably, lighter, and stand out more. I believe that working more in black and white will help you find these errors, which you can then bring over to color once you've mastered it a little more.
Lastly, there's some tricks and tips to drawing faces which even anime (mostly) adheres to. Like how eyes are placed about halfway from the top of the head to the jaw. The gap between the eyes is usually the same width as the eye itself. The mouth from end to end should extend as far as each pupil. The ears are on the same plain as the eyebrows. And many things like that! Keeping these proportions in mind and learning little tricks to facial symmetry will not only help how the expressions look, but will extend to the rest of the body as well. You can read more about it
here!
I think that's a good place to end this now. All artists have a "long way to go" and neither one of us are exceptions to that. Remember to play with things and experiment and not to limit yourself to your comfort zone. But don't break the rules until you've learned them completely either! I can already see a major difference between your earlier works and your girl jumping picture. You're well on your way so I think you've got a lot to be proud of so far. Just keep practicing and keep having fun. That's the most important thing!