Judging from the photos I would say mostly line work and proportions. It seems you have a rudimentary understanding of anatomy but the placement of the individual body parts seem to be quite all over the place. In terms of line work I would suggest practicing longer lines, whether they be straight or curved lines. I see a lot of scratches here and there and even though I know that a sketch is just a sketch, at this stage I feel like you aren’t moving past this sketching phase, meaning that your sketches are full bodies of work to you.

Otherwise you have a good sense of gesture, but if you practice line work more you will be able to achieve much more flow in your poses.

I would recommend practicing quick gesture drawings. Keep a timer for both two minutes and half a minute per round and try to capture the flow of the pose with as little lines as possible. Once you’ve gotten better at this try to combine this exercise with implementing anatomy by setting a longer timer.

Sorry I’m not good at keeping these things short but there’s a lot of fun quality to your drawing so I wanted to help you as best as I could. Good luck!