Camo probably won't go for much. CO2 tanks will only go for $10 or so apiece. Maybe $5 or so for the hopper if it's a gravity fed. Chest protector, it will depend on the brand, but no more than $25 or so max I would guess. Gloves maybe up to $10 depending on the brand. Pods depending on the brand again, but only a couple of dollars apiece if they are just generic. The pod pack will net you up to about $15 or so. The gun, mask and J&J barrel will obviously go for the most. Your best bet on those is checking the BST ads and see what they are going for at the time you decide to sell.
As for the barrel safety plug, most fields don't allow them, so you probably won't be able to sell that at all.
The most bang for your buck will probably come from eBay for a set-up like that. I would post it there if I were you.