If you want to really get good at art my suggestions would be to grab some other books, some ones that can prep you up and get you to understand what you're doin fully, I will PM you links to some useful books and recommend some books you'll have to buy paperback/hardcover but are worth it. The main thing you gotta do is practice, practice, practice, to get good at the human form, the best thing would be to practice drawing still life, hours and hours of that, since most still life is just simple shapes, it helps a lot since well, everything when broken down is just simple shapes and since the human form is just A LOT of shapes, well, definitely helps when you can tackle down an individual simple shape.
You may want to pick up a sketch book and some pencils (I recommend 6b, always have a sharpener with you, don't take an eraser because it forces you to think more carefully about what you're doing, if you do want an eraser, only use it for highlights, use it as a tool, not something to poorly erase "mistakes"), start a journal of what you're drawing pretty much, go around and draw from life, do gestures of people, contours of things and people. Another thing you'll want to do is try to get a good grasp on composition and this means making pieces, planning them out, using reference, etc.
Don't just stick yourself to pixel art, really, pixel art is just a medium, it would be so good for you to pick up some paints or soft pastels, anything, coloring pencils even (the artist's kind though, not the cheap cheap stuff), grab an easel, grab some canvases or grab some strong paper you can draw/paint on, go to work on just making things, you will be surprised on how much you improve since you'll be spending hours on each piece, practicing new things, just ensure you're always challenging yourself, always tackling things you struggle with, etc. Right now I can tell you're fairly new to the process but everyone starts out at the bottom, no one magically becomes a great artist over-night, it takes practice and it takes some of your own individual style, which you will develop not at the beginning, but when you begin to grasp everything and see a clearer vision with what you want.
Look even if you're not REALLY serious about it (but it seems like you are, if you're ordering a lot of art books, coming to Pixelation, etc.), its still always better to have a bit of a grasp on what you're doing instead of having no idea and in the end you have a new talent to show off and be proud of.