Usually the organisers will provide this, but the standard is that you need full leathers (two piece zip together is ok), ACU gold sticker helmet. Bike has to be in decent condition, sump bolt done up tight, decent state of tyres etc.
My modifications to the bike are remove reg plate, unbolt mirrors, remove fuses for lights and tape up headlights.
More here.
https://www.focusedevents.com/terms.asp
It's a bit intimidating at first, so make sure you take it easy. Speak to the instructors, they are great. Make sure you keep yourself fed and watered so you don't get tired, and a plastic petrol can is useful.