The most important item you need is a helmet, which is kind of a given, but gloves and shoes are simple items that go a long way. The benefits of having a good pair of racing gloves and dedicated shoes far outweigh the cost.
In this tech video, Kenny explains why having these basic items will help you as a driver and what the features and benefits are.
Sorting out your tire pressures after the first session is fairly easy if you're using the right tools. The temperature will tell you if you have too much or too little pressure, but depending upon the tire, that pressure could be more critical than you think.
In this video, Kenny's go-to guy for safety, Ben O'Connor from Impact Racing explains what you need to know when buying a helmet. If you buy online most manufacturers provide a generic sizing chart. Ben explains where to measure your head and how to do that, but also highlights some features and benefits to having a helmet that can be customized for fit.