That is an amazing piece of art for your first attempt :O
Hmmm I didn't have a clear 'start' to my art, I just practiced my backside off, would draw as much as I could, and was very fussy on getting proportions exact before worrying about colours/shading. Try working in a variety of mediums to find one that really suits you, and make sure you get a good understanding of light and dark tones. Drawings that are just middle of the range in toning look flat and boring. It's the ones that have a deep black in some sections, and white in others to highlight, that stand out from the crowd.
As for how I got into commission work, I just started by putting my work up on local horse forums. A lady asked me if I'd draw her stud colt, I charged her very little for it, and it just went from there. I made myself a website, and started advertising on horse forums/classifieds. Then I got some business cards made up, handed them around, etc.
It's not easy to get into, it took me years to get a constant stream of work, but at the moment I am working flat out with commission after commission, it makes all the hard work setting yourself up worthwhile