And I can be wrong, but....
From NJ you will most likely be looking for gas in VA.
Exit 104 is a truckstop/restaurant area. Generally lowest fuel price (gas/diesel)
Exit 130-133 (central park) has wawa's (generally low price - goto the 'b' exit vs the 'a' exit) which is sometimes higher than than 104. (you enter VA at about mile marker 179 to judge your distance)
You next stop (again guessing at a generic car/mileage) is in South Carolina. Try to hit something in the middle of the state, those stations/truckstops had the best prices a month ago.
And believe it or not, absolutely use the HESS stations on property @ near MK and DTD. Best fuel prices around @ Disney. Off-site stations have been $.30 higher per gallon.
That said, I am heading down on the 1st of March, so I'll be looking for inexpensive fuel myself.
(Spirit air rocks, AC airport is generally a walk thru, smaller airport, cheap fairs too...)