Before you find your art style or even start anything, start studying anatomy so you know how the human body is structured/built. Afterwards you´ve done that, I would recommend you studying colors and shading. There´s plenty of YT videos on that topic.
Then, if you´re not going for realistic portraits like the things they teach you in art school, find your art style.
with my drawings I always do the details after done with the outline of the drawing. I also enhance the drawing by traceing the drawing in pen after the details
