YES! Make as much art as you can; create projects for yourself like you are doing with the world you're developing, focusing on what interests you. Post relevant pieces that you feel demonstrate your skill level the best. Update as you improve. Repeat :)

It's not too early to build a portfolio because if you meet a professional, you'll have something to show them to get help. As far as this drawing, what I noticed is that the arms and legs are in the wrong place for someone who is running. Also, the lighting on the painting is not consistent, you need to pick a light direction to determine where the shadows are.

I would say: go ahead and make your portfolio. After some more practice you would make another one and maybe replace some of your drawings or create a whole new one. Also try as many platforms as you want and decide for yourself if this is what you are looking for. Note how Steve Lenze drew the running person. When we normally run, our left hand in front means our right leg in front (opposite sides in front), otherwise it would be a bit difficult or rather not quite efficient? Your drawing is a bit confusing in this small detail: looking at how you have drawn the folds, it seems that his right foot and right hand are in front, even though his right foot seems to have the shape of a left foot? Keep practising!