Cancade,
I waited, but my buddy didn't.
My buddy Dennis bought everything before we started class. His rational was that he wanted to train on the gear that he would be diving with. That was reasonable logic, and it was good for him to get comfortable with his gear.
However, after we got certified and began diving, his thoughts changed. He started seeing other people's gear on dive boats and in dive shops. He discovered what he liked and disliked about his gear. He understood more about what was good and what wasn't good (for him). He refined he ideas about diving and his needs came into clearer focus. He has since replaced virtually every piece of gear that he initially purchased, with only a couple exceptions. (He still swears by the Henderson Gold Core wetsuit and the Apollo Bio-fins) In fact he is on his 3rd or 4th BC and his second set of Regulators.
I took a different route. I rented for the first 9 - 10 months before I bought "everything". Of course I had to have the required personal gear before I started, but the rest of the stuff had to wait.
While we were doing dives, I made mental notes about what I liked about the rental gear, and what I wished that I had. I talked to other people about their gear, and what they liked and didn't like. I looked at gear in shops with a newfound understanding of what I might use and what was worthless trappings.
I ended up deciding what I wanted, and then worked out a solid deal with a local shop. So far I have replaced my snorkel (I think I have about 6?) and the gloves I use for cold water. I have added some pieces of gear, and I purchased some back-ups, but essentially I am using the same gear that I started with.
Now 4 years later I am seriously considering get a BP (or two), and I am saving for a Drysuit. However, my regs are good, my fins and mask are fine.
There are reasonable arguments for both sides of the "buy or rent for training" discussion. It is a very personal issue regarding finances & commitment etc. I would just recommend waiting and learning and then putting the new knowledge to use and buy gear that will provide you years of service without second thoughts.
Just my opinions, and only because you asked.
Wristshot