Hey,
For someone who picked up a pencil a week ago, you're pretty solid ;)
First advice I'd give is to use a greaser pencil (2B is really good). While making a gesture drawing, there are 3 axes you need to focus on in the human body: shoulders, hips and knees. No need to actually draw them, but you need to be aware of them: they give the idea of the movement. Another line you need to be aware of is the "line of action", name of the website. It's basically the line representing the spine of your model extended to the ground.
Although sometimes the line of action is hard to see (like in a model sitting in a 3/4 view) you can just try to summarize the pose with simple shapes.
I saw that you were drawing the hair in your gesture drawing, there's no need to do so: just draw the shape of it (triangle,...).
If you struggle to draw a figure well-fixed to the ground, make sure that the feet of your gesture drawing are positionned on an ellipse on the ground (make your ellipse larger if you're drawing a figure in a low angle view)
Hope it was useful (that was my first critique ever, and english isn't my mother tongue, i might have slaughtered some words :/ )
Have a nice day :)
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