He snared his first commercial commission – for fashion magazine Glamour – with an illustration of a cheery woman atop a corporate ladder under the headline: "Success is a job in New York." He soon struck his own success as a freelance illustrator on Madison Avenue, flogging shoes, hats, handbags, leather goods and sanitary napkins.

It was pre-pop and pre-Mad Men. Before his paintings of Marilyn Monroe, Elvis Presley and Campbell's Soup cans. Back when the iconic artist was better known as "New York's most distinctive and sought-after illustrator of ladies' accessories".

The portrait of the artist as a young man is told in the exhibition Adman: Warhol before pop, at the Art Gallery of NSW. The exhibition of some 300 works – many on display for the first time – highlights Warhol's relatively little-known career as one of the most highly paid commercial illustrators in New York in the 1950s.

"It is a very different Warhol from the one people might be familiar with," says Nicholas Chambers, senior curator of modern and contemporary international art. "I wanted to show audiences a side of Warhol that is utterly surprising but also reveals a lot about what is to come. The show is, in a sense, about the formation of Andy Warhol."

The exhibition, which runs until May 28, includes drawings, sketch books, advertisements, album covers and reproductions of Warhol's playful window displays of perfume bottles. Intimate black-and-white photographs show him mugging for the camera – no match for the suave Don Draper.

The artist who emerges from the exhibition has business smarts and, like any good adman, a knack for making people buy things that they don't need.

While other artists moonlighting on Madison Avenue used pseudonyms to avoid the taint of filthy lucre, Warhol brazenly added his name at the bottom of ads."He was unashamed about the fact that he was a commercial artist," Chambers says. "I don't think Andy would resile from being called a salesman."