I'm actually pretty new to pixel art, too, but I had some experiences and... here is my attempt to help you.
If I say anything wrong, please correct me someone. It's my first attempt on helping someone on this forum.
The Face is a little strange. He doesn't have a pupil on the eye for a three-pixel eye (it's a rule I've made: if he has a three-pixel eye, use a pupil, but I think that's just me being weird), and it doesn't seem to match his body at all (through I think this is just my opinion).
His arms are too big, I think. If you 'open' them straight, they would get near his feet, and that shouldn't happen. Maybe making the arm a little shorter would fix that?
And I think the pose is a little strange. It looks like he is just putting his hands on his waist, but then you realise that you can see his hand, and it is closed. If it's supposed to be a fighting stance, I think putting his hand more near his face and showing his arm a little would make the animation better.
But... it's actually a good animation for first time :p. I didn't know how to shade very well, so I never shaded at all in the beggining, but I see you are practicing it!