This is a really good practice. He's drawn very well and the movement is awesome. The only thing that bugs me with this is the way he's walking. It looks like he's sidestepping. If he was walking it'd be kinda like a fox walking. Front, rear, front, rear. Also, there could be more frames in between his tail movements. It'd make it look smoother and more realistic. It looks very nice and has very smooth line art. I also envy your ability to actually DRAW Toothless. I cannot draw him for my life. Overall though, its a very good animation.
The first thing I noticed about this animation was how much it really looked like Toothless. You got all the details right and its enough detail to know its toothless but not so much detail that it looks bad; its a perfect amount. I did notice a few mistakes on the animation. The inner front foot or the left foot looks almost backwards or to its side. Now, I'm not sure if you did that on purpose or not but the foot should be facing forward or to the same direction that all the feet are facing. The animation is smooth but I think you should have added a few more frames for the tail or decreased the distance the tail swings so it looks smother. Overall this is animation is great, I would really enjoy seeing more animations from you like this.