Exellent work, you are correct in starting from understanding the movement and big parts of the anatomy first (Head - Torso - Hips - Legs)
Keep at it and carry on by adding more to these, always comparing - meaning;
The lower leg for instance, how big is it compared to say the waist? Or the head? So you get the proportions right
Next step for you, Id say, understanding the
curves of the body, see why the skin lines travel as they do... and start adding volume to your sketches, I'd say you're ready already because you've done really good work understanding the movements!!
