The first (worst?) thing that i noticed is the thing espadon already pointed out: quality of the line. Those short overlapping 5 mm lines are the trademark of a drawing noob
. So you have to get rid of it. Ok the noob thing was a joke the real reason is that drawing with the small lines doesnt allow you to see the big picture, which is what every drawing should start from. Also, flow is really important, especially in case of a juicy female body, its curvy and flowy and you want to bring out these qualities, and those small lines just dont do it.
Another thing is that your drawing seem too clean. I dont see the helping constructive lines (for example the AXIS of torso or limbs or head etc). Either you have neatly erased them or you dont use them. If you dont use them then you really should start using them, because not starting from the framework is causing the unnatural angles etc. At school we were encouraged to let these construction lines show, they dont mess up your drawing they make it more of a drawing
And another point: manga is a stylised style, meaning you have to know the real forms first to stylize them. Drawing a dirty old wrinkled man is much easier than drawing a young female, because the latter is much more subtle, and on that accord, you should really start from the skeleton. That gives you a good foundation in the proportions. And you should do quick figure drawing, i mean like 3 or 5 minutes on a figure, just random people in a park or smth will do, this improves your flow and ability to see the whole and stylizing it, drawing only that which is important and defines the figure/character.
Sorry if my text is somewhat jumpy but im at work and had a beer and just thought i post something which might help you, always nice to help out a fellow artist.. but yea youre def improving keep at it
