If you're on stock suspension and don't do much hard driving, I would go 17x7 or 17x7.5 with an offset that's at least +45. With these wheel sizes, the following tire sizes are the most suitable and the descriptions are my opinion of what they offer:
205/50/17: Most fuel efficient; however, you get the least curb protection for your wheels and will have the least grip of the group. Diameter is close to the stock 205/55/16, so gearing won't be effected. I would only recommend this as a winter size on a 17x7 since narrower is better for snow/ice. However, I'm guessing you would use your stock 16's for winter.
215/45/17: Best overall performance size for 17x7. Improved acceleration since the diameter is slightly smaller than stock, creating the effect of shorter gearing. Easier acceleration maintains fuel efficiency. You also get sharper steering response since there's less sidewall, and as a result, a slightly less comfortable ride. I use this size personally on my 17x7 since I value performance over comfort.
225/45/17: Best overall performance size for 17x7.5; the widest that's recommended for 17x7. It will give you more overall grip than the 215/45, but on a 17x7, you'll sacrifice a little steering response but maintain ride comfort. The wider contact patch may decrease gas mileage slightly. Diameter is close to the stock 205/55/16, so gearing won't be effected.
235/45/17: The widest that's recommended for 17x7.5. May give you a little more overall grip than the 225/45, but you'll sacrifice steering response. The wider contact patch, larger diameter, and increased weight will decrease acceleration performance and fuel efficiency, but will give the best ride comfort.
Cliff Notes for 17x7
205/50/17 - fuel efficient and comfort, but with the least grip and curb protection
215/45/17 - fuel efficient with good steering response and improved acceleration, but less comfort
225/45/17 - best overall grip and comfort and most curb protection, but less steering response
Cliff Notes for 17x7.5
205/50/17 - fuel efficient and comfort, but with the least grip and curb protection
215/45/17 - fuel efficient with sharp steering response and improved acceleration, but less comfort
225/45/17 - good steering response, overall grip, and comfort
235/45/17 - sloppy steering response and least fuel efficient, but most comfortable and most curb protection