Some thoughts
You're using some unnecessary colors here. Mostly because they don't have enough contrast between others to have a noticable difference, or you already have similar colors elsewhere.
It looks more as if the button on the ball is spinning around than the whole ball is spinning. It might help to subtly shift the shading and highlights every other frame to imply a slightly imperfect texture that's moving.
What is the intended purpose of the white outline? Unless you're trying to make it look like it has some kind of magic aura, generally white outlines don't work too well. They waste valuable space in the sprite (which you want as much of as possible to convey shapes in a limited space), and, combined with dark outlines, create unwanted banding.
Thank's, I'll consider it all in my next works!
The white outlines are simply because I,as a begginer, saw it in some tutorials and reproduced for no reason other than i found it cool.