the best way to go is Florida to New Mexico, and then North through Oregon and Washington, to Homer, Alaska. Then, Hitting Utah, Idaho, Wyoming, Montana, N. Dakota, and S. Dakota will position me to visit my son in Milwaukee, and then back to Florida via every Barbecue place in North Carolina, South Carolina, and Georgia. If I can control my foot on the pedal, my Scion Xb gets about 35 mpg.
It's a matter of pride, because my daughter has me well beat on states, as right after high school she went around the US a couple of time taveling the rails on freight trains. She also took a number of small vacations (to eat and get her clothes washed) in some of the finest local and county jails for railroad trespass in the country.