I have never been to this site and it really differs between the sites. Some of them provide overalls and full face mask, some just the full face mask in my experience so far. I haven't yet come across one that does gloves or boots or neck wrap.
What I would recommend - take some trousers that are good for sports, ideal some tough ones (jeans are very bad, durable but bad with sweat), some thin protection gloves if you have some but if not don't worry about it. If you have a reasonable wrap for your neck you may as well take it and see if you get on with it, its again not essential so if you don't have an appropriate bit of cloth then don't worry about it, I personally don't get on with neck wraps at all so I just take the welts. Then you absolutely need water and money, for money you need enough to buy some BBs, drinks and food and maybe cabs and stuff depending on your existing fitness, because airsoft can be really tiring and wipe you completely out if you are currently unfit. If you already have an idea of how much water you get through when exercising then take an appropriate amount for the length of game, otherwise count for about 2 Litres for 3 hours of gameplay. It might be more than you need but you are better off having a bit too much. Take at least some of that water in a small bottle you can take with you into the field in a pocket so you can stay hydrated as its not uncommon for games to last multiple hours without a break.
You will go home with marks, bare skin ones from close up might break the skin although its pretty rare and those can take a week to heal. Usually all the marks are gone after a week and through the overalls most wont leave a mark. The site looks like its a mix of CQB and outdoors, so you probably wont get shot as much as people do in really small sites like Bunker 51, and presumably it wont be as hot or as close up. My advice is based on the most grueling games I have had there and what I have found I needed. In the woodland games I take a camelback of water but a small bottle will do the job just as well and other than all this I also take a towel. I use it to dry out my head after a game so that my goggles don't fog up from all the sweat, but you'll get a mesh mask most likely and that wont be an issue for you.