at the marketplace tab:
You can only bid in the auctions using treasury notes and if you sell something the treasury notes that another player bids will be converted into gold.
At the Market there is a man called the "Shady Man". From this man you can get treasury notes, but it will cost you ingredients to get 1 note.
You can also convert your treasury notes into gold by clicking on the hand in the inventory list, 1 treasury note will give you 1000 gold.
...better change all the treasure notes on the page with treasury notes
fixed, Juanaton