I'm going to give my advice on this, though it generally differs from others. If you are trying to get better at drawing quick and loose gestural sketches (which I assume based on your title), then don't worry about line quality yet. You can't really work on both at the same time at first. If you focus too much on line quality now your drawings will likely become stiff. Keep drawing loose sketches by letting the pencil move freely. In time, you line quality will improve while still drawing quickly. Nice work!!

Great work! I would suggest practicing on line weight to help your sketches flow more better and to keep practicing gesture. Hope this helped :)

These are nice! good gesture and tension in the poses, and the proportions are good. My only critique would be that your lines are pretty fussy, I would work on having your line quality help with the dynamics of the poses. The one on the upper left has the nicest lines. Keep going :)