have a 2002 nissan altima burgendy buying rims but what size ?

[Frank]

everybody tells me to buy 20 inch and itll look perfect or 22inch but thats kinda big and also more expensive my friend also is selling me some 18 inch?? how would that look ?what do u think?? and are fenders important u know the plastic cover above the tire is it that importnant cause i dont have one please help