Most successful in DOI or in their own skating career?
In skating terms, in pairs Jodeyne Higgins, Sean Rice and Brooke Castile were ranked pretty similarly in the world at their respective times 10 - 14th although Brooke was US national champion whereas Higgins and RIce were, at their highest, Canadian bronze medallists Maria Filipov was her national champion in ice dance but failed to qualify for the free skate at the one World Championships she entered.
Mark Hanretty represented UK in European Championships and had successes in international comps with his partner Christina Chitwood.
I believe most of the other skaters had successful show careers but did not particularly make their mark in competitive skating outside of their national level. SOrry if I have missed anyone out