Hands can be tough and good on you for challenging yourself. I might try to be really deliberate about grouping the fingers so you get the gestural feel you want. The fourth drawing is really nice because you were getting a sense of planes of the forms - keep that solid feeling going

I'm not sure where you start your forms but it seems to be missing the segments made with joints, trying to add knuckle later on isn't going to fit well. Put your structure underneath first, treat each finger segment as it's own shape and then. Start with a light pressure so you can easily fix any mistakes and don't be afraid to draw threw same pose now than once, and like others have said, progress to smaller details as you go.

Its ok to play around with lines at the beginning until you figured it out, but I would advice you to make soft lines when looking for the form and then practice cleaner lines for the final strokes.

These look good. Hands are hard for everyone! Just keep practicing. Start with large overall forms then start adding smaller forms.