Pretty easy to start. Decide the "flavor" of the round robin. It could be very specific ("$1 chips, plus slot cards and unused moist toweletes from anywhere but Nevada", or very general ($1 chips).

Float the idea here, and see how many people are interested. You hope for 8-12, or whatever number seems manageable for you. Get their names and addresses.

Seed the pot with some reasonable number of the items. Hopefully since this is how you figured out what to trade, it will be easy. If you are using chips, maybe 50-60 of them to start - or whatever you think is reasonable. Send it off to the first guy on the list with instructions to trade and send it on. Do the legwork up front and make the lists, print up the address labels, etc. Makes it easier for everyone.

Then sit back and watch it move from person to person. Eventually it will get back to you (the last name on the list).

You can get more detailed by adding a signup sheet to show who took what and replaced what, or you can make it freeform, its up to you.