You decide but the rule of thumb is about 1,000 credits per $1.00. If you think the item is worth $5.00 you could set GIN as 5,000. However, since you are new you have to have so many completed auctions with positive feedback before you can use GIN. Also, as a new seller on Listia you might want to verify your Facebook, Phone, Credit Card etc. It will increase your bids!