The first and most important thing about modifying a car is stance. You can't just pick any good-looking rim and hope it will look good on your car. Getting the right style rim, ride height, rim size and offset is crucial. Every car has a perfect rim, height and stance that will look best. A VIP car can tuck half the rim and look good, but that wouldn't look so hot on an AWD car. An AWD car would look great with 18" rims, wide tires and a flush fitment. And most FF cars would look horrible with 18" wheels.
Wheel offset is one of the most misunderstood and unknown things about car building. There's a lot more to it than just a number. On any given wheel you will find an ET number. ET standing for 'einpresstiefe', which is German for offset.