Seems like most things are personal choices that we later regret. The things I was never sorry for were: buying a decent BCD with integrated weights. Some folks don't like IW systems. If you buy entry level stuff and later find yourself a few dives a year kind of person than you did right. However as in my case it became an addiction and basic stuff didn't cut it. The straight scoop is to take your time, do research, watch for good buys, don't expect your dive shop to be happy if you ask them to service something you didn't buy from them (e-Bay) and add equipment as you go. I personally don't like rental gear. We were recently on a boat with a novice diver who had a leaky BCD. The dive master told him not ot worry but just keep putting air in it. Man, it's your life! Is he crazy? So the bottrom line is that this gear is "Lifesaving" equipment remember that.
Oh yeah. If you get into photography buy a digital not film camera. One of the biggest mistakes I made.