Default round hard brush is a work horse and can get you most places you want to go. But, if you want to play around with different brushes, a lot of artists have free brush packs you can download and try out for different feels and can emulate traditional media more. The default brushes on adobe sketchbook are very nice as well, and can mimic pencil and stuff pretty good. About your drawing, you're doing pretty good with getting general proportions! However, the eyes are too high up for the overall shape of the head. You might want to check out some videos or tutorials on the loomis head method, and then overlay your drawing over your reference pictures to check accuracy. I did a quick transform of your image and lowered the eyes, made them smaller, and moved the mouth over to align with the centerline of the head to demonstrate.