Most beginner and instructional skaters can skate on a 1/2" radius. A 5/8" radius will take care of most recreational skaters.
When figure skaters get to the level where they are in a serious program, they will be under the guidance of a coach or instructor. The skater should consult these people for advice on the best radius for the program they are performing. Most common is 7/16” to 3/8” for ice dancers and in between for synchronous