I am ordering rims for my cavalier... They are the same size as the ones i have and they fit my stock tires. When i got to checkout it adds a wheel installation kit.
Are these neccesary?

Its comes with chrome lug nut or bolt kit, hub centric rings, and chrome valve stems. I don't want to spend the money if i dont have to. So i just want to know if i need it and if its recommended i get it. Thanks.

hub centric rings = yes
lugs w/ keys = yes (must be 12mm x 1.5mm, make sure)
valve stems = yes (how else are you gonna fit the tire up)

usually when you buy lugs, valve stems come w/ them, well at least mine did

Sounds like discount tire. try tirerack they may have the same one you're looking for and they throw in the ring and @!#$ for free.