Gambill's passion for music was born in Colorado Springs, where his family moved when he was eight years old. He began playing guitar when he was nine, learning on his grandmother's old acoustic, and became "obsessed" with the Woodstock documentary he first saw when he was 12 years old, transfixed by iconic performances from Jimi Hendrix, Richie Havens and Alvin Lee of Ten Years After. He was also informed by his parent's collection of classic rock albums, subsequently discovering contemporary guitar heroes such as Stevie Ray Vaughan. 

A crucial turning point came when Gambill was exposed to jazz at 15, after joining the high school stage band. "The band director gave me an opportunity I didn't really deserve, and I didn't have the foggiest idea what I was doing," he recalls. "But I practiced and worked hard and listened, and I got to be pretty good at reading big band charts, and other guys in the band who knew what they were doing exposed me to a lot of (music)."