Draw whatever you are afraid of drawing. Just keep practicing. Also, check this girl out [link] I know she may now be doing the kind of art you're aiming for, but she's the very best example of 'practice makes perfect'.
The thing is, it has to be a hell lot of practice. Good luck
You know those things that you don't draw because you know they're too hard and they'll look terrible when you do it? Draw those things. Draw from life, draw in black and white, and closely examine and compare artists that you like. Don't play it safe or you will stop improving. Be aggressive in your subject matter, and work your ass off.
If your upload rate represents the frequency with which you draw, then draw more. Make it a habit to at least get one drawing of something or someone done each day. But try at least to aim for about 10 minutes of drawing per day. Several sketches can be completed in that amount of time.
If you want more advice than that, I refer to the link in my signature.
Practice the fundamentals. Draw basic shapes (circles/spheres, cylinders, boxes/cubes) draw cubes in one, two and three-point perspective from all different vantage points, draw simple objects flooded with light from one side to see and understand graditation of values, and draw from real life.
Some people stress anatomy which is clearly quite important for figure drawing BUT I would say focus on proportion first. Don't worry as much about where the muscles will bulge and twist. Focus on the proportions, like the length of the arms in comparison to the body, head to torso, etc.. It will train you to see proportion and more importantly see when something is out of proportion (looks off). You can take that skill to all other subjects (trees, pop bottle, giraffe) and it will be a great foundation for anatomy. If you understand lighting, perspective, proportion, basic shapes, etc.. Anatomy will come easier. A muscle is drawn by considering the lighting and the underlying shapes. You can certainly still practice anatomy but I wouldn't put it as top priority. There are underlying fundamentals that will help you draw EVERYTHING better, that will also help develop your anatomy skills. It's all about the fundamentals. Good luck.
Try drawing things you wouldn't usually draw. Draw things from life, draw things realistically, draw landscapes or still lifes. Draw things in different mediums. It might not be stuff you are interested in or would ever do again - but it makes you think and inspires you with ideas that you can take back to things you want to do and if you take it seriously you can learn new skills that you can apply to whatever you want.
You won't ever know what you are capable of unless you try - but stick to your comfort zone and you won't ever learn about anything outside your comfort zone...
I can see potential in your artwork. However, you should try drawing more fullbodies and backgrounds instead of head shots. I see that you're starting to do that more; and it's good, but you should also study shading, coloring and anatomy. The necks you draw are too long, and the poses you draw aren't very fluid. This can be easily done by looking at references and practicing gestures!
You're also drawing things facing the same direction. Try drawing them in a different direction. Sometimes when I draw characters that keep facing right, I spice it up by drawing them in the left direction. Simple things like that makes your gallery look less repetitive.