Alaifia has SWAMPS most technical trails. There are not just straight paths to any of them, although within the trail systems you can find straight sections. Alafia's easier choices would be River Loop, Rock Garden, and Sandpine. Although, as with any mountain bike trail system, that can be deceiving. There are places with big drops, hearty climbs, and lips to get air off of. It's not a good idea to ride here by yourself.
Boyette has somewhat tamer trails, but then again, there are roots, switchbacks, and off camber trails that can keep you on your game. In the East end of Boyette are the more technical sections of Abyss and Imp Gulch. These have hefty drops and climbs that have good momemtum to get you up the other side. Also good to have a ride buddy.
Morris Bridge trails are yet tamer, but then again the roots, sand, switchbacks make you pay attention.
Croom, with the most miles of trails, has it's own inherint issues to watch out for. There are places to get air, but as far as "jumps"? Hmmm, if you're looking for Free Riding you will find that at Santos near Belleview/Ocala. Wear your gear. Bring a friend.