Less offset puts the wheel out further which gives you a more favorable geometry for handling. (But, taken too far, can overload wheel bearings, so you'd be wise to stay within 10mm of the stock offset)

You also need to consider fender clearance on the outside and suspension clearance on the inside.

Look at what you have on the car right now. Find out what the width and offset is. Measure your clearances inside and outside. A little quick math will tell you what will and will not fit... give or take 5mm or so.

You'll need to consider both the offset AND the width of the wheel, and what size tire you intend to run. Ultimately, wheel offset and tire width are what you need to know. (assuming that you're sticking with a tire size that keeps close to the stock tire diameter)