Looking pretty good, except for some things. You should get some profi pencils if you want to draw or a drawing tablet. Both are comfortable but the latter option saves you of spending more money on ink and a printer.
Another thing that I don't like is the nose, they just don't look good. Kishi's been inspired about that one, no doubt. Yet again, it's your work so you decide.
Signature: 7/10 (the colors are too fake and the render doesn't have any link with the background, the border should be 1 px at most and the text is pretty simple, you should try to integrate both render and text into the background, give it some depth, contrast and light!)
Try something new, something you have never done before.
Bring another artwork of yours. Then proceed comparing those two pieces side by side and see differences between them, how to improve both. Even after you finish them, there WILL always BE room for IMPROVEMENT, remember that. Mistakes can be corrected even after you finish the lineart or coloring, it doesn't really matter.
What I'm trying to say is that no matter how much you struggle during the process, it won't affect the design one bit. It might just ruin your idea, actually.
Ever thought about 2D art? If not, give it a go. It's relatively easy and it might come in handy should you decide to move on to bigger things like... comics, doujinshi's etc.