I could do just the PSD, and you can get someone else to help put it through EmoFuri (non-commission of course)~
Assuming you want a commission that looks like Lani, I’d estimate the price to be $60, since there is a bit of extra work involved. But, if you wanted a regular waist-up, then it would be $50.
Cel shading can honestly be more difficult until you have the hang of it. To get the shadows to look right, you have to cut down more defined shadows efficiently. So, really, I would recommend studying realistic shading first.
An important thing to keep in mind is the type of material you’re shading. Different materials have different levels of reflection, contrast, bounce light, penumbra, etc and shading everything the same way can make a painting look boring. Example: chrome is pretty much reflections warping around the shape (tube, sphere, etc), whereas a bright yellow cotton shirt will have no highlights and low contrast.
You must consider the strength and number of your light sources. A sun high in the sky on a clear day will yield harsher shadows than a small room lamp.
Another thing to keep in mind is that you have to portray the overall shading first before thinking about textures, which is an extra level of shading on a smaller scale. Get the big things down before you start working into the little things.
I hope this helped!