>>294402Np man, it's great that you're interested. What national park? Not very familiar with the UK but I can google it
You don't really need all that much. For day trips, which is what you should start with, some food, a few water bottles, a good map of the area, and a bag to put it all in. Comfortable, practical shoes. If you're worried about breaking an ankle, bring boots, but sneakers are usually fine (especially if you're on trails). Where whatever's comfortable, just bring a layer of warm, water-resistant clothes and keep them in your bag until you need them.
As long as you're not going somewhere super remote, there's really not too much preparation/equipment required. Maybe you'll fuck up - bring too much or too little food, forget your camera, get your feet soaked early in the hike. That's great, because you're not endangered by the situation and you can learn from those mistakes.
More than anything, just go and enjoy. Explore and be curious. Good luck dude