Do your research before rushing out and buying a gun. Revolvers are good as far as ease of operation, but limited in capacity. Semi autos have the capacity but operation can be somewhat difficult (not impossible but require more training in operation). Glock, S&W M&P, Ruger SR9 & Springfield XDM are four semi auto handguns in 9mm that I suggest. It is only a suggestion but they really top the market in ease of operation and reliability. Go to an indoor range that rents handguns, explain you’re a new shooter and ask for a basic introduction lesson to go along with your rental (some will, some will not). Rent the handgun, along with eye and ear protection and purchase your 9mm ammunition and a target from them.
Do NOT fall into the trap of buying a gun then and there. Ask if you can rent two guns on the same visit and have a note pad and pen to put down your likes and dislikes. Next visit do the same with the other two guns. Then go home and look at your notes and make your decision.
Along with the gun you’ll need a good gun belt, holster, mag pouch, (I like International Handgun Leather at IHLUSA.com) eyes and ears, a baseball cap, ammunition (try OATH ammunition at OATHammo.com) and cleaning supplies.
THEN most important go and get yourself some TRAINING from a qualified trainer in the basic handling of a firearm, most quality ranges and clubs will offer or know where to direct you.
After this you should START to learn how to shoot, moving on to how to tactically shoot, finally how to FIGHT with the gun. After doing all of this you are now ready to really learn more about your equipment and more importantly to have a warriors mind set.