I really like the super simple stuff you do like the piece bellow.

Some problems that I see throughout all of these pieces are the hands. They're not that well constructed and takes away some of he charm your style has. So yeah put some time into studying hands and how to construct them.
Also, render the forms of the body more round. A lot of your more render pieces have edges reading as hard rather than a soft wrap around to the back.
Last are the faces. All of them have a very flat quality to them. I've seen the stuff you've done in the past and you've definitely improved. But they're still far from perfect. Seeing how you're aiming for an anime-esque style study your favorite artist, how they manage the face, mix in some more traditional stuff so you can learn about the planes of the face and learn to draw the face from many different angles
Well thats all from me, hope that helped.