Getting the best helmet you can afford is the best investment you can make.
My helmet saved my life. Literally.
It was a Bell Sport 2, which was a snell-rated helmet. It took the full weight of me and my kart several times at high speed. Despite a demolished clavical (you shoulda seen the xrays) and multiple lacerations, bruises and contusions I had ZERO head/neck trauma and no concussion. The paramedics were utterly amazed that I wasn’t in worse shape than I was.
That helmet was also really handy in deflecting the nuts and bolts Mansfield left on the track ;-).
I’m not trying to endorse Bell over others, but after what we went through together I wouldn’t hesitate to buy another one.