Burning Man runs on Gift Economy, not on Bartering or on any monetary system. Money usage is basically not allowed (except for buying ice on Camp Artica or Coffee on Center Camp).

You will receive gifts, and are absolutely not excepted to gift back, but to ‘gift forward’ to other burners you like. Bring gifts. Stuff that is useful on the playa and are not moop.

However, my advice for first timers is always to not worry too much about this. It’s difficult to anticipate what all this sgifting economy is about without having visited the Playa previously. Bring some useful stuff and carry it with you. Give it to somebody you like, or somebody you think will need or enjoy your gift. And enjoy and appreciate what you are given and give it to somebody else or dispose it properly in case you don’t need it anymore.

Here is a good selection of stuff that are always appreciated and useful at Burning Man.