Take the MSF class first. Depending on your State you may need to have your permit before hand (not sure about CA). You will find all the gear you need for the MSF class in your closet (boots, long sleeves) as you will be lucky to hit 20mph in the class. Most classes supply helmets but that was the once piece of gear I bought before the class.
Getting some riding gear is the next step as it is hard to ride your bike home without any. Insurance will factor into what bike you can afford, especially for a 17 year old male, so make sure to check out the rates on the bikes that interest you before buying.
I disagree with madjak on the heavy pair of jeans. Those will not provide adequate protection (either impact or abrasion) on any slide at speed. Everyone comes to their own conclusion on how much gear is enough but for me it is everything; boots, pants, jacket, gloves and full face helmet.