Another critical part of your MTB are the pedals – without them, you’re going nowhere. Mountain bike pedals need to be very grippy to keep the rider’s foot in place. If riding a downhill trail, or doing jumps, go for flat pedals to have maximum surface area in contact with the sole of your shoe.
Many XC riders like using SPD (Shimano Pedalling Dynamics), which are a very popular clipless pedal, as it gives them more control and they can put more power into the crank. It’s largely down to personal choice but don’t forget to make sure your cycling shoes are compatible with your pedals.