I'd give you the same advise I gave @peter-hartnett, you can take a look at the post I left in his topic if you're interested 
Basically, it should be easier to do the lines of actions and skeletons of the figures before the actual silhouettes. What I can add is that by doing that, you can find the position of the limbs and joints more easily, and capture the right proportions. It's much easier to think about the position of simple volumes (lines, egg-shapes, cubes, etc.) rather than full-fledged arms, legs and torsos with curves and details that distract you from the structure
I hope this is helpful!
