It depends. Some people get bad scarring because they have skin that scars easily. Some people get bad scars because they had infection or made some mistakes taking care of their chest. There's no way to say you'll have no scarring/little scarring. There are 2 general surgeries: peri, and double incision. Peri tends to have less scarring since the doctor just cuts around the nipple and stitches it up around the nipple. Double incision cuts around the underside of where your pecs are.
Transbucket has pictures of different surgeries by different doctors so you can get an idea as to how people turn out post op.