Let see here a helmet is the most important, I've been knocked out a few times with the helmet, go knows what would have happened with out it.
Next is boots or you are going burn you leg, and burns hurt. Also where at least jeans.
After that I say goggles to protect you eyes and gloves to protect your hands. A chest protecters help a lot, other than that, thats all you should need.
Also don't forget to ride with someone incase you crash or your bike breaks down.