did you use anything like adhesion promoter or something 10-15 mins before spraying to give the paint to stick to? What color?
Your best best for most of the plastic is to find the dark grey/black interior to swap in. The carpet can be dyed (or replaced) you recover your headliner, the seats can be covered or swaped out for something nicer which if you have a base model might not be a bad idea for some support.
As far as colors, I like my interior to clean but also like it could have been stock. I might shoot for a gloss black instead of just a flat/textured. I think colors are fun but they get old after a while and everybody knows you painted it at that point. You could also get that 3m wrap stuff, there is a guy that does it here (not that its cheap) but you could get some crazy carbon fiber patterns if that is what you were looking for.
Now if you have some crazy dash/door work then I'm all for color paint because you want that to be seen, stock stuff still is stock no matter the color.