First off, the walking test. You can't get a good idea about your walk by having him walk in place.
Notice the clear limp, which is because you use an odd number of frames. With an odd number of frames, there's a subtle speed difference between the two feet, hence a limp. Having a walk without a bob also tends to feel very stiff.
Pixel art wise, never pixel on a white background. Steve looks very pale and it's because of the background, it tricks your vision. Try using a neutral grey color when you're starting out with pixel art.
There's a bunch of other stuff to go over, but let's start with these basics