The phrase most likely means that Jephthah led unprincipled raiding parties into the towns and villages of Gilead. These were unsavory men, a band of freebooting guerillas led by a social outcast.
1 Jephthah comes across as a gang leader, happy to be surrounded by those who validate him. But as socially undesirable as Jephthah may be, he is a survivor, a brave man, and a seasoned fighter.
3 Then Jephthah fled from his brothers and lived in the land of Tob, and worthless fellows collected around Jephthah and went out with him.