Great job! Gesture drawing is a good way to start, and i'm glad you've put in effort into it. I'd suggest using more time in your sketches though, I realized that my ideal time is around 120 seconds, and 30 seconds often rushes you and makes you make quick decisions you may not be happy with. I think you should work on big body shapes too, I appreciate the head, chest, and hip area shapes, they're good and accurate. Keep sketching! :)
I like the way that you started off with a charcoal pencil as a way to challenge yourself,and how you started with your gesture. I do have something to suggest. I suggest you draw a circle for the joints. So like where the hips,elbows,shoulders,knees, etc. go to make it easier to map out on the body to make it easier to sketch the proportions later on.
Nice work on more of your 30 second drawings, Amurphyr, yet I've got one most smallest idea: Why don't you do another 60 second (1 minute) sketch, please? The reason why is because you'll be much more better focused on the lines of rhythm. I really hope you'll find it essential, vital, and crucial in your next study.