Rims

Great to be here
Im glad to join so here is my first post
hey , i just had a question that i was hoping that anyone could answer because no one else nor do i have the time to find the truth. I plan to get 18" rims but keep on being told by tire places that the highest i can go is 16" for my 96 dodge avenger
i know that they are not right but just wanted to make sure
if they do fit can anyone recommend a tire size

any help muchly appreciated
Rigo