Hello Pilot, do you do any visual measuring (that thing where you hold your pencil up and measure)? It helps with seeing how far away things should be from each other. It looks like you already have some basic shapes of where the knees, shoulders, head, chest, pelvis and elbows are on the body. From there check the distance between those points. As an example is the knee to far away from the pelvis? Is the foot to far from the knee? I hope that makes sense. It's best to do that kind of measuring with the longer poses, because you have more time to really study the image. Happy drawing! : )
Here are two videos on the subject that you can apply to the human form.
This is a pretty good start for your gesture classes. :) Do you have any 30 and 60 second gestures to share too?
To get better at proportions, I think a good step between drawing the action lines and then the outline of the figure is to compartementalize the figure first. Right now, you have a loose action line going through the body with some joints drawn that don't really connect together how they should, and you build the figure around this. Each bodypart is its own shape, and it connects to other shapes in pretty specific ways. Your gestures don't show this process and it can hinder your progress to get proportions right.
A good example are mannequins, they have solid shapes like the ribcage and pelvis, but they're connected by the joint of the waist - the ribcage and pelvis are able to move separately from one another, and if you draw the underlying shapes and connect them with the joint, you'll be able to get the proportions between the two correct more easily with time and practice.