All your gesture drawings look pretty good! I definitely recommend, if you can, doing that first as a part of your daily routine. even if its just a few for 10 minutes.
I think your next step should be studying the 3 basic parts of the body (Head, Ribcage, pelvis) to learn how to find them and how to draw them as boxes, and then using that knowledge to do the assignments. it's what's helped me the most. Proko has a few videos on that with the robo bean, also Moderndayjames has a few good videos that can help. Dan Bearshaw has a lot of videos on that stuff too with a lot of info.