This is actually very good for your first thing. I like how you're already learning to dither so early, and you did it good. Look at my avatar, and you'll realize why I'm going to call you Doomraider Jr. =P Ok, so lets start off with the basic c+c.
Lightsource:
From what I can see, you KIND OF have a light source, mostly on the body it is correct, but not so correct on the feet. from where the light is, only the tip of the front foot should have light on it, the lower part being a bit darker. The foot in the back shouldn't really have any light on it, except for the area in the bottem right. This is because his foot is behind the body, and some light is reaching the back of the foot. Other then that, you should shade it with some dither of the darkest red on there.
Shadows:
The foot should be casting a shadow onto kirby's body. also there should be a lighter area below kirby's mouth, but a darker above it(very small though) to show that is mouth has some depth.
Lineart:
The lineart seems fine, except for the jaggies. Jaggies are when your drawings arent curved smoothly and it created a rough rigid looking line. if you made all the lines smoother it should look better.
Colors:
Im not going to lecture you on the color count as you're brand new to this stuff. I like how you got some unsaturated colors there, but for kirby's body, you should've had some more virbrant pink because well, its Kirby! =P Also I should mention that there are 3 black pixels, I don't know if they were intentional though, considering not all GIF savers are perfect.
Overall, this iss an awesome piece for your first post, I'd like to see some improvements outta you!
Keep on pixeling,
-Doomraider