Protection is a must.
In the begining knee pads. Your going to get pulled over the front plenty.
later on as you get more confident, cash pant's will save your ass. Cos you will miss time it, and the kite wont always hold you up. You will feel this even more if you wear a waist harness.
Eldow pads for hard surfaces like grass. Though a body armour jacket will work better. A Bummer in the summer, as it will get hot.
All-way's put a lid on it. You never no when it will happen, but if you are pushing your ridding, sooner or later your head will slap the ground. Also wearing a lid is the most visual sign to other's that saftey is important.
As for wrist gaurds, i've had a few moments wear i would have liked them, but for the rest of the time i feel that they would have given me more problems with kite control, and this is the formost in saftey.