So, a friend gave me a prompt challenge, and I'm generally getting to the point where I'm not exactly sure how I need to improve. Just that there's plenty of room for it XD
I just dunno how to get there atm.
Any advice is appreciated!

I think this is a cool piece. There are a few things I noticed though. The biggest thing was the anatomy of the character. Her right leg is huge. The knee shouldn't reach up to her face.
I did a quick paint over to show a few things.
Sorry for the face change isn't close enough to your style

I tried not hiding the anatomy to much so you can see it. Areas I feel you should look into are 1. the anatomy and proportions(even the way i did the right arm can be fixed. Don't copy that)
2. the folds of the clothing
3. being the sky background. and
4. the colors.
You did a good job with her expression and I like the simple design. The design elements are working well. She has a cool hair style. The lighting seems consistent as well. Honestly I think using reference here would've helped a lot in this case because she is a kinda difficult pose. You have to be good at fore shorting and knowing the anatomy of the leg being raised up like that. As well as how the skin bunches up when sitting on something.
Hope this helps.

Thank you for taking the time to do that! No worries about the face, lol. Just a style difference.
I see what you mean about the leg and also the muscles, since you painted them. Also the folds, I see what you changed, and it makes sense.

I'm going to try and fix the picture a little more to include those changes and make it better.

I see you also mentioned improving the sky background, I think I see what you mean there. I need to work on backgrounds in general.
I did want to know what about the colors you thought should be different?
Thank you very much for taking this time ^_^

Glad it could help somewhat/ Here's what I meant when talking about colors. Sorry I didn't include it.

With the hue not being as varied enough, you get this plastic look. What this piece needs is some Sub surface scattering or SSS for short. There are videos that better explain this than me. Marc has a video explaining this here

Okay! So I touched up a lot of the parts you had pointed out:
-I fixed that knee right after you pointed it out XD, much better now.
- I adjusted the colors of the skin after watching Marc's video, but I think the hands had maybe too much red?
-I also tried to make my anatomy better, specifically in the arms and legs to show some forms. I still have a way to go, but I do like how much better they look with some form in them.
-I also adjusted some of the folds in the outfit to make them better, also more like one of Marc's videos.

I know there's more growth to be done, but I do like what I was able to improve with your help, so thank you very much for your advice and your time! ^_^

glad it helped. This looks a lot better than before. Your on a good track now.