Usually I would put cel shading first, just to block out the colors. If your character is standing in direct sunlight then they would have harder shadows, and if they're standing under a cloudy sky or a dim lit area then they have softer shadows. Also I typically make the gradient between light and shadow have very saturated/strong colors so it doesn't turn out muddy (in a brightly lit setting)

Interesting take, TikkiFalls, and I agree. But I'd also like to add... If you're just looking for a smoother way to blend colors, choose colors that are close to each other on the color wheel. For example: if yellow is your base color, use orange before red for a smoother transition. Then you wouldn't get such a rough finish like you drew here.
It's also important to note that you should be turning shades darker with each darker color you use. Orange is darker than yellow, so make orange a darker shade than you did with yellow, if that makes sense.
I'm not good with technical terms, but I hope this helps!

@tikkifalls @Mewsea
Thank you both for the feed back, and excellent advice!