1. A helmet is a must. You could go for a pisspot/BMX style but you get hot in those. A good MTB one is fine
2.Shinpads are a great addition to have. It does hurt a lot when you dig your shins on the pedals
3. I tend to use downhill gloves as they are really tough and the palms have less padding, so you can feel more of the bars.
4.Go with either skate shoes or proper MTB/Trials shoes. They are designed to grip and do a far better job than trainers.
This next one may sound odd but,
If you wear any rings then take them off before riding. My wedding ring really digs in when I grip the bars.
Buy some hand cream, because your hands are going to get really sore.