Water
Oh the essentials of life which I always underestimate. Now your site may have water and you may be able to get unlimited amounts, but then again your camping adventure may not include water or you may have to find water. Either way I would highly suggest bringing water and lots of it.
Ok, so you are glamping and you have an RV and there is a water spigot. Ok, but it may not taste great. I would suggest if nothing else at least get a water filter for the RV. Having water bottles are a pretty important backup plan.
So it is suggested to bring 2 gallons of water per person per day. Now, this isn’t just for drinking this is for cleaning, pets, showers and whatever else you might need water for. So a three day camping trip with a family of four need 24 gallons of water, which is a lot. I prefer to get the two gallon jugs and also get a site with a water source. That way I can bring a couple jugs and refill them a couple times a day. You can also go with the pack of 24 water bottles which is about 3 gallons of water, but they are harder to refill and easier to over drink.
The other thing to consider about water is the possibility of being on a trail needing water, but only having a stream nearby. This is where items like Life Straws are useful. They allow you to drink directly from a contaminated water source and it will filter it as you drink. Sounds gross, but if you need water…