Further to the renting, if you can hold off on buying for a while, you can learn more about the gear you may want to own on the long run. I bought so much stupid gear that I ended up selling again because in the beginning of your diving career, to quote one of the more infamous diving instructors in Canada "You don't know what you don't know."
Agreed, which is why I've been holding off on the expensive stuff. I had a good idea of what I was looking for in a wetsuit/fins/etc after talking to a bunch of experienced divers.