Standing in searches is determined a lot by both the SEO terms you use, the popularity of your items, and how recently they were listed and relisted. Popularity has to do with the number of views, favorites, sales, and treasury inclusions your items have.
My items rise a lot in search results with promotion. It has worked well for me to join promotion teams, treasury teams, and Pinterest teams. I also share links to my items frequently on twitter and Facebook to generate more views.
Search ads have never worked for me.