An excellent first attempt. You have all of the basics down by the looks of things and can now focus on picking up the more tricksy skills that will help you improve. You also picked an Ork as your first mini to paint, which makes me like you! Greenskins are the best!
Wow, i wish my first stuff was this good! An excellent base to move forward with. A few more intermediate layers on the horns between the base brown and the lighter bone and/or some lining to make it look more like horn would make this much stronger. Certainly something you are technically capable of and would make a good improvement!