First of all you have to take into consideration that stock footage category is a really huge one with tons and tons of different videos. You have just 8 items published. About stock footage I think that the top sellers have a big amount of items uploaded, so the customers have many options to choose and the authors have more chances to appear in the search results. My idea is that you should make many many more items to get sales, diversity. Today, every market has too many authors and too many items for sale.
I guess that´s the best advice for your category, produce and produce and produce more.