Oh right, if you want the 3d shading style like kirby, then you'll probably need to make your sprites a lot simpler. If not, then solid colours like I suggest will be the simplest way to get something looking ok.
Your plant is a great design, but maybe a little lop-sided. I like the shading, although some areas are a bit messy, like the shadow under the petal onto the shoulder. If you want to have lighting, make sure you use a consistent light source, and not just shade everything as if a light were shining directly from the viewers eye. Here's a repaint I did, showing some simple lighting and removing all the AA.
But again, I'd recommend to just use solid colours with either no lighting, or just simple solid shading (with one or two bands).