If the baitshop caters to both salt and fresh anglers, they are likely to have:
fathead minnows, AKA "tuffies"- good community species, peaceful and easy to breed, males have nice black and white pattern and gnarly tubercles
golden shiners- good community species, peaceful and attractive, similar in appearance to tinfoil barb, but get too large for a 20 gallon tank
gulf killifish, AKA "bull minnows"- good for rowdy hard fresh/brackish tank with other big killies
mummichogs- see gulf killifish
sheepshead minnows- see gulf killifish
There are probably other species they carry too. Bait tanks also often have "stowaways" including other killies, mosquitofish, minnows, sunfish, etc. Try to buy baitfish the day they come in to the store, and hit them immediately with Jungle Labs Parasite Clear or similar. They are likely to be stressed and parasitized or sick, so don't be surprised if you have a high initial mortality rate.
If you want to wild collect fish, there are lots and lots of cool species in central FL, in both inland and coastal areas. There are only a few of the minnows, darters, and catfish that make up most of the fish diversity further north, but you have a plethora of killies and livebearers, pygmy sunfish, true sunfish, and small euryhaline fish like hogchokers, pipefish, gobies, sleepers, blennies, etc.