Was the Gadarene demoniac a Gentile or a descendant of the tribe of Gad?
The Gadarene demoniac was a descendant of the tribe of Gad, not a Gentile. Gad was one of the tribes that settled east of the Jordan River, so dwelling in that region did not make him a Gentile. The name Gadarene itself begins with Gad, identifying his tribal connection.
Les teaches that during Christ's earthly ministry Jesus only had anything to do with two Gentiles: the Canaanite woman and the Roman centurion. When people object that he forgot the maniac in Gadara, whom Jesus delivered from a legion of demons, Les says he was not a Gentile. Although the man lived on the east side of Jordan, Les's stock answer is to ask what the first three letters of the word Gadarene are: Gad. So the maniac of Gadarene was a descendant of the tribe of Gad, which lived on the east side of Jordan. That fits the earlier point that Gad was one of the two and a half tribes, along with Reuben and the half tribe of Manasseh, that stayed east of the Jordan rather than occupying Canaan west of the river.