MacGill was born in the Perth suburb of Mount Lawley and began his first-class career in the 1993/94 season playing for Western Australia. Both his father, Terry MacGill, and his grandfather, Charlie MacGill, had previously played cricket for Western Australia. He was an AIS Australian Cricket Academy scholarship holder in 1990–1991. He managed just one game, against New South Wales at the SCG but did not take a wicket and did not play again for over two years. When he returned in 1996/97 it was for New South Wales and he took 6 wickets in the match, the first being Darren Berry. He finished the season with 16 wickets at 37.00.