Gary began his remarkably successful career in advertising and marketing. He first joined Charles Haines Advertising, then Nestle, leaving in 1971 to establish Colenso Auckland. During his 16 year tenure with the agency, he was Managing Director of both the Wellington and Auckland operations.

In 1987, Gary founded Outdoor Heritage (now Rodd and Gunn), selling the exclusive Rodd and Gunn and Logan labels.

He was a founding director of Dress Smart and is a former director of Michael Hill International Ltd and Sheppard Industries Ltd.