Carp can be deep fried like any other fish but you must scour the fillets to break up the bones. You can then eat the fish bones and all, but ofcourse still be careful. Carp are also good on the grill, keep the skin on and grill them skin side down. Baste with hearty flavors like mesquite, bbq, teriyaki, etc. Then pick out the bones as you eat them. Unfortunately Carp can have a strong earthy taste to them, so marinating them overnight in "bright" flavors like sprite, 7up, etc, will really make them taste alot better. (Same for any fish btw.)
Please only eat Carp under 10lbs, the best eating size is 5lbs for sure.
Buffalo taste incredible and to this day are one of the most popular commercial fish in Texas. And chances are Buffalo is what you're eating at any typical buffett. Cook them the same way as Carp, but they have lighter tasting flesh so you can also use sweet and sour type sauces for this fish. Again...on the grill they are superb. Perfect eating size, 5-10lbs.
Forget Alligator Gar, stick with Longnose Gar if you want some good eating Gar! The flesh is white, boneless, but... a little more softer, spongy compared to other fish. So the flesh of Longnose Gar is SUPERB for patties, gar balls, etc. Boil small chunks in Crab Boil until they float, dip in butter, cocktail sauce and enjoy!
When it comes to Catch & Eating rough fish, you REALLY and I mean REALLY need to research ahead of time what your plans are. You don't want to bring home any rough fish from stagnant waters. Plus keep in mind the population where you're fishing at. Taking home a mess of Carp from Joe Pool (they taste good from there btw!) will NEVER hurt the population for instance.
Longnose Gar are doing well and are available pretty much anywhere in the DFW area, you can take as many as you want (for tablefare) and never hurt the population. Perfect eating size, pretty much any.