Depending on the traffic that the marketplace and the product range in which your campaign is set for, it could be almost instant. If you set a bid in the auction that is the highest bid set amongst your competitors, your ad will win the auction.
From here, you will gain impressions as your product is listed in a prominent position on the page. As long as your listing is of good quality, you should expect to see a greater number of clicks on your listing and in turn the possibility of higher sales.
Auctions are reset with every page load, so if the category where your product is featured receives a lot of customer traffic, then more impressions will be made. Impressions equate to the number of auctions you have won. If the page where your product is listed has very slow traffic, then the impressions, clicks and conversions will match this.