Just wondering if anyone could give me advice, this is my first texture, please give advice

use 512x512 or 1024x512 resolution, next time

as Punk said, bigger rezz or screens
also try to make it less flat and edgy using various tools for that depending on your software

Possibly use a different program. I suggest Gimp 2.8.

You can't do much shading until you do that. Work on mapping, use a 512x512 or 1024x512 template as a background to help make it centered. You won't be able to do much more until you use a better program than Microsoft Paint.

for the type of the head his trying to make i'd advise using adobe illustrator instead
though you'll need alot of software research but as soon you get the basics it'll be easier for you to make awesome textures *cough...cough like me...cough cough*

Use photoshop or Gimp.

And use 512x512 sizes.

For become your frist head, it´s okey.