Impressive studies! It reminds me of when I first started as well.

A couple of things I wished I knew when I started out, hopefully they can be of use to you.

1. While learning the muscles is vital, don't forget that skin exist, and will determine how detailed the muscles are drawn.
2. Don't forget about the perspective of the bottom of the feet, being aware of this will help you with placing characters in a 3d space.
3. Be wary about burnout! If you start to get tired, take breaks! Remember that you need to do this for the next couple of years.
4. When you study, try to immediately apply it to a new piece. It'll help you retain the things you just learned.
5. When doing gesture studies, always try to identify the leg or point where the weight is placed on.

Your line weight seems to be developing quite nicely.

Keep it up!