Hello and welcome to Pixelation, Heterostraca
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The first thing I noticed with your piece was that she had no hips. Obviously if you're not going for accurate anatomy, it's not much of a problem; however, it's always good to know how it would really look, so that you know what you're warping, and how to convey the feelings you're going for most effectively.
Control; right now your art is all over the place. You've got wonderfully billowy folds on the skirt that are rendered so sweetly, you've got the sketchy head and arms with the basics plotted out, and the contour lines for the leg. It's good to work on the whole thing at once, so that you don't get caught up in the details of the dress while everything else is still in the design stage. Just don't stick your head into one spot and stay there forever; jump around a lot to help keep the piece unified.
I really like the fading away leg idea! It should be pretty cool. Just a suggestion, but I think that adding just a couple more buffer colors with the same width as the fade lines would make it look wonderful.