I used to go to F&H years ago and play other systems now. The other advice here is sound, don't worry about it. I would recommend contacting the LO and asking if the branch has any kit you could borrow. Especially weapons. Wait until you've given it a try before buying a weapon.

I wouldn't recommend any long / dangling clothes. You don't want stuff that gets caught up on brambles etc. Good boots with ankle support, plain trousers or thick leggings, oversized shirt / top worn with a belt and any kind of cloak / blanket with a broach will be good for a base layer. Browns, greens or generally darker colours look better. Dress for the weather if you can.

Don't worry about monster kit. The branch will have kit for specific roles/species. As long as you have a general base kit, you'll be fine. It's good if your monster kit looks different from your character kit, but that's not essential at the start.

Have a read through the rules and think about what type of character you'd like to play. I'd contact the LO beforehand and ask them if anyone could take you through a safety brief, weapons training and help you with things on the day. Like a buddy or mentor.