Just what kind of a clothes hound are you? Most restaurants are accommodating to casually dressed tourists - and that would be the only place asking for dressy clothing. Pack 1 nice size bag with slippers, docksiders and sneeks - take a sweater or jacket, and I suggest that you buy a new sweatshirt there rather than taking one with you - 3 pair of shorts and 2 pair of long pants or jeans should do it. If you need more- support the local economy and shop there - prices are reasonable if you shop. Don't forget your friend's addresses. In July, you could wear shorts and a light sweater or mid-weight shirt and be comfortable during the day. At night, especially if you take a cruise, slacks and a jacket are in order. If you like to sleep with the windows open, don't forget to put a blanket on the bed. You might not start out with it, but you will probably end up with it. Don't forget any medications that must be ordered by your pharmacy. There is a RiteAid in the shopping center that could probably order from a prescription already registered in another of their stores - check first. There is a hospital just outside of town that can handle normal emergencies - I wasn't overly pleased with the facility, but I'm spoiled coming from a major city. Even men should get acquainted with the fanny pack. It locks around your waist and can hold all kinds of little things including a cell phone, Put a handkerchief and a bandaid or two in there. There is plenty to see and remember - so any photo's or video taken will be cherished. Campers know what to pack. There are very few beaches in this area because the water is so cold. Even in July, you could use a jacket. Plan to drive south to Freeport and go into LLBean. There are no locks on the doors because they are open 24 hours a day. There are great shops there. I usually do all of my Christmas shopping while there and then I ship it back rather than try to take it onto a plane or overstuff my car.
Go north to Camden, especially in the winter and use the tobaggen run. Last time I was there it was fifty cents a ride.