From my experiences you won't find much gravel in fl. Mostly sand when you get off road. The bigger tires will float on top of a lot of that. Around Ocal is a mountain bike paradise called Santos. It is very popular and is supposed to be the bomb to ride. Near by are some rails to trails. The Withlacoochee trail is a nice paved trail. There is also the Marjorie Harris Greenway near Ocala. A lot of the state parks have bike trails, so you should be able to find something to ride on.
This website might help you make some of your decision.
https://www.bikeflorida.net/