I think different things work for different people but for me I agree with the previous posters, I got 31 and just used the free resources on the LNAT website and online. I started practicing a few months before my test, a couple of hours a week and don't think spending any money would have helped me. Its not like A levels where you can study as such but there are things you can do ofc.
I think it's crucial you know how the questions are structured and practice these under timed conditions at home. I used the whiteboard you're given at the exam centre and read the passage then wrote down, A,B,C,D for each question and crossed them out until I was left with one answer and went with that. (I could usually score out 1 or 2 quite quickly and this method stopped me going over and over needless info)
Don't neglect the essay section practice, especially if this is important for your chosen uni. I also practiced this a good few times at home under timed conditions. At the exam I used the whiteboard again, quickly choosing the q I felt most comfortable with and made a diamond with Q at the top, argument(s) for to the left point, against to the right and my conclusion at the bottom. How much time you want to spend on this depends on your typing skills, I'm pretty good so spent about 5 mins on the whiteboard and the rest typing and easily got 600 words. I felt this way was best for me, felt confident when I was writing and that my essay was well structured and had everything it needed.
Things I wish I'd known before I went? Silly stuff like I wish I'd tied my hair back as they need to see in your ears. Ditto that they take your glasses off if you wear them to examine them. I also wore leggings which I was glad about as if you wear anything with pockets, they have to be turned out (jackets, bags, etc all already in the locker) None of these are major obviously but if you're nervous you want a smooth entrance. Make sure your passport is signed too, loads weren't and they check. Just silly stuff like that. You literally can't take anything into the test, no water or anything just yourself 😆
I've read lots of posts about reading newspapers etc in the run up to the test and while I like the news and read papers online this really didn't help me. Part one is all about knowing the format and part two was ethical/moral/debate topics and I don't think personally it's a test on current affairs anyway, more how well you can structure a balanced argument and provide your conclusion.
People do pay for arbitio, buy books and even pay for LNAT tutors and if you think this will help you and you have the funds why not but I don't think it would have made any difference to me, I either "got" it or didn't and I don't think you can actually study that.
Good luck with it!