Look up some of my old posts. I wrote a great deal about the pluses and minuses of the various options and with pictures. I've owned and dived with both. Briefly, hookah is nice as you don't have to carry tanks. Two qts. of fuel, if you run a gasser, will last longer than you want to be in the water. But...the noise of the gas engine and the compressor itself will anger all those around you enjoying the area. Electric is quieter by far, but you have to get those heavy batteries lugged around. Simply, the heavier the battery the longer the machine will run without recharging. J Sink is the best gas powered machine. Hookamax is the best electric machine. Brownie's comes in a distant third for lots of reasons. The major advantage of an electric machine is the pressure regulator switch on the air accumulator tank that tells the compressor to turn off when the tank is full. Maybe 10 breaths later it's down to the pressure where it needs to turn on and it runs for a minute. Gas machines run all the time. Read everything you can on all the websites and you'll have enough info to make a good choice.
Dont's- Don't use hookah until after you have taken the training to become a certified diver. Don't try to build one yourself from and 'oiless' compressor. You gonna build it yourself get a compressor that's made to provide air for breathing...not changing tires. Don't use hoses made for automotive use. Buy the hoses designed to pass good air to you and not some of the contents on the inside of the hose. For SCUBA they recommend you have your regulator serviced yearly. (Depends on use and care you give it) The hookah regulator is no different. It's just built to run at a lower second stage pressure. Don't forget to have it serviced. You are going to get sand, mud, and lots of other stuff into the working parts of the regulator because it's the closest thing to what your are digging for except your hands. Don't do deep diving, that's over 8' in my book, without Spare Air or a bail out bottle. And you are going to want to add about 5 pounds more weight than for 'regular' sport diving as fanning the sand or rocks to get the bling pushes you back and away from the direction you are fanning. Experiment with the 'search' function on this site and you'll gets lots of input from a bunch of folks. When they all say similar things, believe it. Hope that gets you started. jim