tips on how to improve

I would watch anime and pause on a scene I liked and redraw it. Or draw my own point of view on it. Or draw people on T.V in anime form. Or my friends lol

Uh! Those are hard. I think for that in particular, you're gonna need to understand how hands are constructed, break them into drawing blocks or something and just practice a whole bunch. Get references to help you out.

Hands, well lets see. You can only see two parts of the thumb outside of the palm. The pointer finger is usually shorter than the ring finger for men. Opposite for women. The hand bends in the middle.

The most important thing I learned BY FAR is to always start a sketch with the torso. NEVER start with the head and then draw the rest. Everything on the body moves based on the torso's position so it's ten times easier to place everything correctly if you start with the torso. Think like this; when building a house, you don't start with the roof then build everything else. The foundation(torso) is primary. Hopefully that helps.

with hands... just look at your own hand while drawing and do that very veeery often :D and I also start with the torso but there are cases when I just start from the head haha

I wouldn't do it if you're only using pen. You'd normally add textures on you're character's skin, but they're expensive, so only use them on final products. If anything, you could try making your character 'look' the ethnicity by giving it certain defining traits. You could also use manga creation programs to add them digitally if that's the way you're gonna go.