Pretty Good! I would say you should work on practicing the curving of your lines. Like you said: "too sketchy". Though I think using"sketchy is a bit vague here, we have to narrow it down a bit. The length of your lines are good but they're too straight, and because their too straight, you tend to go over them over and over again (because things in the real world aren't made of straight lines) which cause this 'sketchiness'. So yeah, just practice drawing really curved lines that are curved at various degrees. You can practice drawing really curvy lines, or slightly curvy lines, and try them all from different angles so your arm gets used to it. If you keep on working on that, now you have a larger variety of lines to choose from when you sketch which can limit sketchiness and give you more confident lines. Try to keep in mind how many times you're going over a line you've already drawn. The less you lift your pencil off the paper the better. Maybe even try some pen sketches too in order to limit your "sketchiness".
I think your lines are quite good, the problem seems to be that you don't know how to use them effectively to show the action. First of all, be aware of gravity. The body constantly works relative to it, especially to maintain balance. Start with a clear torso mass. What is it doing? Next, draw the action of the limb(s) that support the torso's weight. In standing poses that would be the legs. Get their placement right and make sure the figure is balanced. Then draw the action of the arms, neck and head.
What you can do is instead of drawing the whole body, you can try stickman figures. What i mean by that is try to draw lines that connect one form to the other in one sweep motion for example one line to respresent the whole arm and another to represent the connection between the both arms and so on.
Try to imagine the flow of water in the pose that you drawing, where the water will crash and turn or where it will flow swiftly. This way you can draw stickman that represents the gestures.