Please I want to know how can I know tags used by top sellers of my similar gigs ?
Does your work? Just navigate to Fiverr.com take a look at a few gigs to get a general idea.
Using your gig as an example, the tags are below the gig page
However I will advise you only use it as a guide. What works for them doesn’t necessarily work for you. Gig placement is very complicated. You can do your personal research to know what tags buyers put in the search box by trying to find your own services. You can also research on Google to have an insight.