You already have boots and that is by far the most important equipment to own yourself. Improperly fitted and/or worn out rentals are very painful on the feet and will take away some enjoyment on what will already be some difficult learning days. I have always recommended you rent the remaining equipment until you have gone a couple times. You do not know yet if you will even like snowboarding, you do not know what type of riding you will enjoy doing, so in effect buying equipment now is buying blind. If you do choose to buy first, buy a used board and bindings or something new from a couple seasons ago. You will most likely want something different next season so dont spend too much money. I also feel that a hybrid/rocker design is best for a beginner as you will spend much less time catching your edge and taking flight.
I would venture to say that its far more important that you have proper clothing than anything else. Staying warm and dry on the mountain is absolutely vital to your enjoyment. You MUST have waterproof pants, jacket, gloves, goggles, thermals, warm socks, face mask or scarf, etc. I have ruined far more days from getting too wet or cold than from improper board and bindings. When I started skiing in the early nineties I wore jeans with schotchgaurd spray and a regular jacket and i could never finish the afternoon. ;-)
The most important thing is that you go out and have fun, never give up, and never look back. Good luck!
Last edited by ThirdManWalking; 12-13-2012 at 07:28 PM.