So there are 53 numbered Black Star Promos. There is only one of each card except for #51 and #52, which have stamped versions from Pokémon Center New York. They have the same number and are differentiated by the stamp.
Outside of those, there were “miscellaneous” unnumbered promos released during the WotC era, like Ancient Mew, Prerelease Stamps, and tournament prize cards. It is easy to collect all of the promo cards released during the WotC era, the numbered Black Star Promos are just the core set.