What kind of camper for trip around the United states

well I guess what we are looking for is something that is a bit more gas friendly..right now we are in the PUP market. We have decided we are not worried about the full bathroom option, as most campground have decent bathrooms. Except we have a 3 year old going to be potty training. We are kind of new to the camping scene, as we are more into the BOATING scene here in florida!