I am so excited to go camping, and while I have some supplies ready, I am in need of some more. 
How fun, I'm going camping too! I also have the basics, I'm just looking for some additional to address some specific needs for my trip 🙂
I am planning on bringing my family on the trip, and both of my sisters are currently pregnant, so they are hungry all the time. I think I could use quite a bit more food for my trip.
Oh dang, I'm looking for food too! We're camping in a pretty dry, desolate place with little food source, so we need to be prepared. Maybe to try and be fair, I could give up more of the food for you if I could have more water in return. 
That sounds like a good idea. Water is pretty filling. 
ha ha ha, that's funny :) So maybe I could give you two food, and I'll keep one. And I can have the water to make up for the lost food? What is your status on firewood?
Well I will need one water. So I think 2 food for me and 2 water for you.
I'd be fine with that, then I think I will need 2 firewood, because I only have one food and will need to cook whatever I can manage to find. 
Ok. That sounds good.
Ok cool! Glad we could reach a deal