I'm a big art person so I'm going to critique. It's VERY good for a first time. I'd pay lots of attention to the shading. You did very good with not making the outline of the horse darker than the shading which is something most people don't get until a LOT later. So very good job on that :)
Try and make your shading more blended together rather than sharp lines, unless that's truly how it was in the picture. I'm guessing, as with most equine pictures, there's a ton of subtle color change and shading involved which can get pretty confusing. What I try to do is imagine the picture in greyscale and think about how it would look if there was no color. Like, what would be darker. (I'm assuming this was referenced from a picture?)
Very very nice job on the bit/bridle. Good attention to detail.
As for the ears, horse ears are wider at the base and finely curved towards the top. Sometimes lightly taking your pencil and tracing over the picture helps to get the idea of the shape of the line your pencil should make when you replicate it on paper.
The forelock is a bit..blocky. Try making quick strokes to replicate the look of individual hairs. A tip I have is that just because there are tons and tons of hair strokes, you don't have to draw each one; just enough to get the point across.
Overall it is a FANTASTIC first try. Good job!
PS: I personally think you got the big hunter look you were going for rather than a pony look.