Helmets - it doesn't matter what other people prefer , find something that fits -that's what matters . The AFX gets good reviews from the webbikeworld people , I have no reason to doubt them , it is reasonably priced and has a face shield , buy some goggles as well then you have 2 choices .
Boots - as you are going off road, buy motocross type boots , broken limbs aren't funny .
Gloves - take at least two pairs , wet gloves when it's cold are miserable .
Consider heated gloves and a wiring harness to fit onto the bike . See warm'n'safe website for details . A "dirt" bike should have enough power to run them - perhaps . Have a look at "hippo hands" if you're going to ride a lot in the cold [ or make your own ].
Joe Rocket is adequate at best , have a look at BMG website for reasonably priced gear ,also consider Firstgear stuff if you don't want to pay for high end bike gear , look in Advrider flea market for used quality stuff as well .Get some good overtrousers for when it's cold and armoured ones for regular wear .
Buying good gear can be the difference between having fun and being thoroughly miserable .
Good luck !
Blessed are the cracked, for they let in the light. - Spike Milligan
"When you come to a fork in the road ,take it ! When you come to a spoon in the road ,take that also ."