Born in Adelaide, Australia, he traveled extensively, first to Europe, then as a journalist based in Whyalla, Perth and Canberra before emigrating to Vancouver, Canada in 1981. In the 1980s he worked as a reporter and editor, first for the Vancouver Sun, then the CBC, where he specialized in documentaries about resource development and First Nations. In 1986-87, he spent a year in Paris as a fellow of Journalistes en Europe.
Gill was president and founder of Ecotrust Canada from 1994 to 2010, when he was appointed founding Executive Director of Ecotrust Australia. Gill served for over five years as a director of Vancity credit union.
He is the author of three books about the west coast of British Columbia including Haida Gwaii.
- Hiking on the Edge: Canada's West Coast Trail (1995)
- Haida Gwaii: Journeys Through the Queen Charlotte Islands (1997)
- All That We Say Is Ours: Guujaaw and the Reawakening of the Haida Nation (2009) (Shortlisted for BC Book Prize and nominated for the Roderick Haig-Brown Regional Book Prize) 
- No News Is Bad News: Canada's Media Collapse - and What Comes Next (2016)
- Confessions of an Innocent Man (writer) (2007), winner of Gemini-award for Best Biography
Other selected titles include:
- Transplant Tourism (CBC) (writer) 2003
- The Boys of Buchenwald (History Television) (writer) 2002
- To Love, Honour and Obey (CTV) 2001
- The Life and Times of Dr. Henry Morgentaler (CBC) 1999
- The Dealmaker: The Life and Times of Jimmy Pattison (CBC) 1998
- The Life and Times of David Suzuki (CBC) 1998
- Mordecai: The Life and Times of Mordecai Richler (CBC) 1997
- Whisky Man: Inside the Dynasty of Samuel Bronfman (CBC) 1996