Born Annabelle Gold in the Bronx to Russian Jewish immigrants Solomon and Rose Gold, Gamson studied dance with Julia Levien, a pupil of Anna Duncan, from ages five to twelve. She then attended the Fiorello H. LaGuardia High School of Music & Art and Performing Arts and the Professional Children's School. She also studied uder May O'Donnell, Helene Platova, and at the Katherine Dunham School. By the age of sixteen was already making a living as a dancer. In 1949 she made her Broadway debut in the Richard Lewine's musical revueMake Mine Manhattan at the Broadhurst Theatre. She returned to Broadway the following year to appear in Morton Gould's Arms and the Girl at the 46th Street Theatre. Shortly after that production closed, Gamson moved to Paris to study under Etienne Decroux. Gamson returned to New York City three years later in 1953, at which time she began to appear regularly with the American Ballet Theatre where she notably danced the role of the cowgirl in Aaron Copland and Agnes DeMille's Rodeo. She also worked performed with Anna Sokolow on Broadway and portrayed Sonya in the original production of Rodgers and Hammerstein's Pipe Dream. Gamson also worked as a dancer for several television productions during the 1950s. On November 21, 1958, Gamson married conductor Arnold Gamson who was at that time the principal conductor of the American Opera Society. Arnold left his position at the AOS in 1961 to pursue a conducting career in Europe. The couple moved to Europe and lived and worked their for the next several years. During this time they began to have children. In the mid-1960s, the Gamsons returned to the United States and settled in Westchester County, New York. Annabelle spent the next several years devoted to raising their children, Rosanna and David, who is a record producer renowned for his work with Scritti Politti. In the early 1970s, Gamson continued with further studies under Levien, focusing on the work of Isadora Duncan. In 1974 she presented a highly lauded program of Duncan works at the American Theater Laboratory in New York City. Critic Rose Anne Thom wrote of her performance that,
"Through her extraordinary performances, Gamson gave audiences the opportunity to understand and appreciate the craftsmanship of Duncan's choreography, forever doing away with the rumor that Duncan's dances were improvised. To generations of dance lovers, for whom Duncan was a legend previously accessible only through writings and artistic representation, Gamson imbued the dances with a musicality and dynamic spirit that, while never intending to mimic Duncan, gave some sense of what was essential in Duncan's choreography and the apparent spontaneity of her performance."
Following this critical success, Gamson drew further acclaim for her performances of the works of German expressionist Mary Wigman and American choreographer Eleanor King. She has also presented a number of her own pieces and has spent much of her time teaching younger performers.