Knees pads? What are you pole smoking or something? Hahahah.
A full helmet is must, or so I say. And I've almost been killed on my quad. I have the works and always ride with my helmet, goggles (but those usually come off unless i'm racing and have a few peal-off's on) and gloves and Riding boots. Usually wear my riding pants a jersey too but not always. When I'm racing I have all the gear on w/ the camel pak too. Gotta stay hydrated. Gloves on the hands and you'll notice no blisters and you'll actually go faster through the brush. You'll get a part of boots the first time your foot slips off and you wrap your ankle back under your axle.
I have a lower back brace and chest protector too, but only wear those items when I'm racing. It's all to each its own but I am a huge advocate for always wearing your helmet. Its not worth it to not wear it.