My First Attempt At GFX

[DustyPorViva]

Which is exactly why you don't dither metal? You also don't pillowshade it...
And what does it matter if cartoons are done on a computer or not? Lighting and shading is the same no matter what the medium of art, except for abstract perhaps. It's one of the first things an artist learns.
I really, really suggest taking a trip to pixel-arts.org and looking through there at their tutorials and such.
And why are you dismissing dithering? What's wrong with trying to optimize colors? What's the sense, and logic, in going crazy with colors just because you can when you can easily replicate the same thing with dithering, perhaps to a better extent. I mean, all in all, dithering perhaps has lost some of its effect that it had a few years ago... but it is in no way a 'cheap excuse' in any way.
All in all, I don't follow anything you say as though you really know what you're talking about.