What advice would you give someone playing their first game?

It's okay to use a rental. I've known lots of people who've bought guns & kits and such before ever playing, encounter difficulties and end up not enjoying themselves and never come back. There's nothing wrong with using a rental for the first game. They're used & maintained to be a quick plug-and-play. If something breaks, you take it back to a marshal and they'll give you a new one for the day rather than you having to panic that you just spent £300 on a gun you can't use. My first personal RIF was an ex-rental M4 from my local field. I used that for 3 years, with no issues, never broke, never had any issues, and shot really consistently. I haven't used it now in probably 5-6 years, but guarantee I could put a battery in it and it would work like I bought it yesterday.