Fort Wilderness is the best deal of all the Disney on-property accommodations. Still, it is expensive. It is convenient since you can use Disney transport direct from the campground. However at peak times (eg after the fireworks finish) it can take a while to get a boat to a bus to your site. I always find Disney service second to none, but then you are paying top dollar.
Just outside the parks near Celebration is a campground called Tropical Palms. We spent several winters there and liked it a lot. For that you would need a vehicle to get into the parks (and pay to park it).