Well, needless to say, I absolutely love this piece. It's actually my current phone background, and one of the better of the Fennekin fanart I've seen. I like the style of this, with the sharp edges on the Pokemon itself, and the softer, warm colors on the ground surrounding it. Fire Spin (I assume) looks just amazing. I really love the way you draw fire, especially how there are some little flecks of flame coming off of it. It almost looks like lava in some places, which I really think adds to it, making a cute Pokemon seem really badass and intimidating. I would suggest that you make the illuminated part of the ground reach more towards the bottom of the page, seeing that the Fire Spin would illuminate that area. I also feel that the "ear hair" shouldn't be as sharp looking, and be textured more, and so should the tail. The tail looks like a solid mass, so maybe some lines for texture wouldn't hurt.
Besides those minor things, I genuinely enjoy this piece, and wish you the best in your future endeavors as an artist.
I can't wait for Gen 6, and I also can't wait to see more from you as an artist.