A big reason to upgrade your stock wheels to aftermarket is to make your car look better. That said, getting stock offset is a no no in my opinion as no matter what wheels you get without a flush look your car won't look good, So if the stock offset is +45, you should look to get less than +30, ideally with staggered setup. Eg for 18s, i would get something like +25 in the front and +30 in the rear (18x8, 18x8.5).