depends on use really , myself only doing the very odd track day , i bought on in lidl/aldi for about €40 . obviously the bottom of the scale but does the job .
You will pick up a good helmet on adverts or donedeal. Shoei or arai are top of the line. Htc are good too. I bought a good quality shoei like new with clear and tinted visors and with pinlocks to stop your visor from fogging even got a bag for 170