I agree with most of what has been said, but if you are looking at nitrox in your future I wouldn't go the titanium route. IMHO, that is a lot of money (they generally cost more) to spend on something to save a couple pounds and there is the, albeit controversial, issue with using titanium regulators with high o2 content mixes (esp. >40% deco mixes).
I know Mares specifically warns against using their titanium reg with nitrox and AFAIK, the Atomic M1 is the only reg they make that they advertise can handle >EANx50 (and it's limited to 80%)...the T1 has a warning not to exceed 40% mixes.
Here's a recent thread that covered the same question:
http://www.scubaboard.com/showthread.php?s=&threadid=19144
I think it boils down to the following:
1) mask, fins, snorkel...may as well buy them.
2) regulator
3) you already have gauges
4) BC
5) wetsuit
6) tanks (probably not necessary right now)
So on the wetsuit, regulator, BC decision you can go any which way. If you are hard to fit and have trouble renting wetsuits (or an aversion to wearing something someone else has urinated in) you may want to get that first. The others are right on about the regs and BC...however, since you already have your own console, it is going to either 1) not get used or 2) be a PITA to switch out with rental 1st stages each time you rent. I would probably get regs next so you can permanently attach your own console to them.
Whichever way you go, welcome to the board and good luck!