Hi, I wanted to chime in here because about 3 months ago I was just about where you are (my wife and I knew we wanted to try scuba, but that was it)....
So, I hope this helps you:
My wife and I scheduled a Private "Discover SCUBA" dive with the LDS. The private session was only $25 each and if we decided to purchase mask, fins, snorkle, and booties that money was counted tword those purchases. After the Discover experance we were hooked! We started hanging out at the dive shop just about every other day, asking questions, and I felt like a bit of a pest, but eveyone was very nice and very helpful. We ended up purchasing our own gear set (less tanks and weights) as a package deal. Our LDS carries Aqualung/SeaQuest mostly and all thier rental gear is this brand. We were able to try on other brands they had, but in the end we liked the Aqualung/SeaQuest stuff the best, somewhat because it was a bit cheaper than the other brands they carry, but mostly because it was solid gear, and reasonably priced when compared to prices I reasearched on the net. (note I'm not advertising here, just pointing out that you should research the gear you like!). My wife and I ended up with a price tag right about $1200 each (BC's, Regs, Octo, Gekko Air/Nitrox Computers, hoses, etc.).
We have also purchased our own wetsuits (some people just don't like rental wetsuits and my wife is one of them).
First, you'll find that you can accumulate gear on an "as-needed" basis. For example, our first purchase were 3 mil shortie wetsuites, for use in "warm" water (pool, mexico, etc.) while we were doing our confined water pool dives. Then before our OW check out dives at a quarry, we knew that we'd be diving past the thermocline to the nose of a 727 (Mermet Springs in IL), so we purchased two 7/5 full suites and gloves and hoods. So as we needed some things, we researched them and purchased them.
90% of our purchases have been thru the LDS, because they had the product we wanted, and it was priced resonably. But I had done enough searching on the internet to know about what the price should be at. On things like Hoods and Gloves, they were way overpriced, so I just ordered those online.
Now that we've been certified and have a few dives under our belts, I've started purchasing things like knives, lights, saftey sausage, etc., but again, I did't get them until I needed them for a trip (we're going to cozumel in the fall, so I'm slowly buying what we'll need to do the dives we want to).
There are two schools of thought here. 1) Rent your equipement to get your cert. and get comfotable with diving 2) Purchase your own gear and use it while your doing your cert.
My wife and I did #2, but we had done the "Discover" dive, knew that this is something we wanted to make a part of our lives, and went for it. We found it was pretty nice to have your own gear in the water to get certified on, since it's adjusted and setup the way YOU want it before every dive.
OK I've rambled on a bit longer than I wanted too...
Hope this helps you out!