Helmets - These come in a variety of sizes and the best way to measure your head is to measure just above the eyebrow with a piece of string. Once measured lay the string out next to a tape measure and you’ll have the circumference of your head (where the helmet would sit).
Knee and Elbow Pads - These can be really beneficial for anyone learning new tricks. Think about it like this, when learning you’re prone to take a few slams whilst pushing your ability. At least with pads you can prolong the session by protecting the joints that are most likely to endure impact when falling.
Shin Guards - A life saver for anyone who slips pedals often. We’ve all done it and instantly regretted wearing shorts that day. Nowadays many brands are producing shin pads that are virtually undetectable underneath jeans such as Shadow’s Invisa lite range.
Ankle Guards - I would recommend ankle guards to anyone starting out learning tricks like whips for example. Just this small piece of protection can lengthen your riding career. That may sound quite drastic but believe me if you hit it once a session overtime that piece of bone will grow and you’re likely to keep hitting it.
Bike Pads - These can be seen as safety or style Either way they do offer some protection when riding. The bar pad of course will help to save your face or teeth when you over cook a jump. The frame pad is great for saving your crotch but also for tricks like tabletops if you’re prone to hitting your shin on the top tube.
Overall wearing protection whilst riding will never reduce the risk of having an accident but when you do have that unexpected one, you’ll feel thankful afterwards having had the pad take the majority of the impact for you.