Green’s Dictionary of Slang

1. (Aus. teen) one who attends a rock concert or similar event.

1999

G. Seal Lingo 105: Other terms of current – that is, mid-1990s to late-1990s vintage – include: [...] gigsters or punters are those who attend such events.

2. one who performs at concerts.

1995		Alan Price [bk title] A Gigster’s Life for Me.
1996		Pol’s True Trooper Travel Tales 🌐 Trooper has never played in Princeton, nor have I with the dozen or so bands I have circled the west with. Certainly every gigster has driven around and marveled at this countryside but rarely do we get to meet any people here.