Carry a lot of underwear, socks, etc to last at least half of the trip so you only need to stop once at a Laundromat. Forget flying across country with kitchen gear. You can buy the basics dirt cheap at Walmart or the dollar store and either keep it or throw it away at the end of the trip.
It is probably too late but I would have recommended making reservations for any National Parks you want to visit. At this point you might have to settle for reservations in the parks but you should reserve nearby.
Due to the heavy, heavy crowds in all outdoor rec areas since Covid, I would recommend laying out the entire trip and reserving for as many nights as possible. I have no idea what you want to see in the East and middle of the US. I drive through those areas rapidly, typically 500-600 miles a day. For a new RVer plan on no more than half that. I stay at Walmarts, rest stops, truck stops, etc, while on the road. I don't plan those in advance.
For the East coast, I would recommend Cherry Hill outside of DC and take train to visit the Capitol, Smithsonian, art galleries, etc. Williamsburg is definitely worth several days in you have any interest in Colonial America.
I am not sure about insurance but suggest you start with your regular car insurance agent.
