Hi Vicki.
I use promoted listings in my other shop, where they cost me about 5% of a sale. I do not use them in this new shop. Promoted listings work well for items that already sell well, so until you have got your basics (SEO, photgraphy, descriptions. brand and policies) fully fledged out and working, I would not recommend using them.
The above link is good. My main tip is that do not automate the bid. I set it very low. It just means that I get more views later on in the day, after the high bidders have expended their daily quota. People who buy first thing in the morning usually know what they want to buy, so they probably have favourited you before and slept on it, so you already have that sale. People who are browsing and buy quickly are more likely to do it later in the day.
