hello from Irvine, CA.
For your first few trips, I suggest just bring some food and drinks. Take a look at what other people's equipment others might have. The best thing about going in as a group is you won't have to carry the kitchen sink. When I plan trips with my friend I tend to ask them what they are bring so I don't bring the same things.
I would recommend getting a FRS, CB or getting a HAM radio as one of the first items if you plan on doing multiple group trip. nothing worse than not knowing what's going on.
If you are into doing your own exploring, then I say the following items are a must.
1) First aid (more than the stock xterra kit)
2) Tire plug kit
3) Air compressor to fill a flat tire, doesn't have to be fancy, i used a cig. plug tire pump for a long time before I got my onboard air system.
4) basic tool set. Check Sears or harbor freight for a mechanic tool set. Also if you know your vehicle have a specific tools, that you might need (like a wheel lock nut) bring it. It sucks having a tool you need stuck at home when you need to make a trail repair.
5) a good flash light
6) I recommend those heavy duty rubber floor mattes. Not only do they keep your truck clean, but when you turn them over and throw it under your tire, it will aid you in traction when you are in a bind. (specially if you are 2wd)
That's what I would start with. If you are free and can go to cleghorn, you should, I am sure there are many season individuals that are willing to show you what they carry. For your first trip don't worry about bring stuff, I usually am the Kitchen sink guy since I have a truck.
If you have any questions, feel free to ask. again welcome.
