ABC Stores: You might be wondering what that is. It’s a perfect tourist store found all over the touristy parts of each island. You can get anything you might need for your trip there. Their prices aren’t horrible (they could gouge more than they probably do) and they are friendly. Books, drinks, food, sunscreen, beach mats, etc. Everything you need you will find there. But you won’t find them when you get away from the main tourism hubs.
Costco: The best place for gas (but it will take a while, just get in a line and wait – the line will go to either side of your car, so don’t worry about which side your gas tank is on). It’s also a great place to get some food at the food counter (same prices as the mainland on pizza and BBQ). Also good for bulk items if you’re staying on island for a while.
Depending on the island you’re on you’ll find Walmart and Target as well. Some place you might only find a local grocery store (and that’s probably going to be a lot more expensive).
Outlets malls… high end stores… etc..