Hey there! Good stuff trying new things, and you are right, something is off and you dont understand how the hand works, but that is to be expected! You just said this is the FIRST TIME you tried drawing some hands, you are learning and that is great!
I reccomend really studying the planes that make up the hand first, just some simple constructions of boxes, rods and balls is a good place to start and to begin thinking about the motion of the hands.
Since videos are helpful, here is a link to a nice introductory method of drawing hands, I like this guy Mark Brunet, there are pleanty of people that will show you the same technique.
&t=32s
But, after you watch that you can also watch him punish himself for 12 hours doing nothing but drawing hands, practice makes better!
&t=36s
For the full figure, I recomend placing the collar bone on your figures next, they seem to be missing a bit of that structure that helps define the upper rib cage so well.
Your attachment points for the arm on the front of the body look great. However I recommend studying the angle of the curves and muscles near the armpits on the back views a bit more, specifically the Teres major and the posterior parts of the deltoid.
Hands are looking good, I rather enjoy the way that you are drawing them. Perhaps paying a bit more attention to the outter plane of the hand on the pinkey side, there are several of your sketches where it seems like there is an extra plane defined on that part of the hand that seems excessive. The two on the bottom left, and one on the top right. But again that is a very minor critique, the structures look very sound.
I reccomend adding some line weight to make the skin folds feel a bit more like skin folds. Put heavier thicker lines on the surfaces that are away from the light, or just on the bottom of the foot, and use a lighter line for the skin folds and anywhere that the light would be hitting. It creates an exttra feeling of depth very quickly.
As far as the position of the toes, you were either working off of images with very odd positioning, or you just need to pay closer attention to the angles of the toe nails and silhouette a bit more. They don't look wrong, so much as just held unnaturally. Again line weight can help to define those parts more as well. Try doing a thicker line for anything that is in front of something else, that can trick the eye into thinking there is more perspective in the image.
When it comes to choosing to focus, its a good idea, but you have to make sure that you are not burning yourself out. So pick something and focus on improving it, but be sure not to kill your love of ddrawing.
When it comes to faces, they are one of the most difficult things for humans to draw, you need to destroy a part of your mind that has representational shapes for what you "Think" a face looks like, build up what reality is, and then come up with how you want to enhance reality (or just go crazy and do photo realism). So it is important that you KNOW that faces are hard first, really take that to heart and accept that it will take time.
A very popular way of drawing the face and the proportions of the body/head was developed by Andrew Loomis, the book "Figure drawing for all its woorth" is very good and includes both gesture, anatomy and facial anatomy. Most of the people that teach any drawing of humans teach an adaptation of that method, even if they don't realize it. And of course Loomis didn't really create it, but he has one of the best and earliest books on it, so he gets the credit.
Keep at it and have fun! Love what you do and keep doing it ^^
I recognize the images that you are working with from the poses, so thats definatly a good thing.
Since you are looking to get into storyboard and animation, I would recomend focusing even more on the relative position of the hips and shoulders, find the tilt between them and experiment with pushing it even a little bit further. Many of the poses that come up in the gesture drawing cycle are pretty static images, so perhaps try taking what you see and pushing the movement (angles and stretches of the body) further, see if you can hit a point where its "too much" movement. I am just thinking about animations where the artists pushed the movement to 11, Dead Cell animations, Kill la Kill, one punch man, in all those cases they push the movement so far that its not even vaguely human, but it looks AWESOME.
