Green’s Dictionary of Slang

a dismissive excl. used in any context where the speaker wishes to show disdain for the previous speaker and their ideas, suggestions or opinions.

1985		Indianapolis Star (IN) 10 Feb. 5G/2: Get a clue (NC) - an admonition directed at one who is not current or not paying attention; same as get a life.
1996		R. Rendell Keys to the Street 190: ‘Oh, get a life!’ said Valerie, slamming the area door.
2002		Confused posting 14 Nov. on ‘Ghost Recon Team Ladder’ at Rumble Forums 🌐 You’re like the lame retard that follows ranger around and has his nose up his ass. Go get a life and put the bong down, you get dumber every damn day. I remember why I left this game now, too many tards such as yourselves.
2016		Observer (London) Mag. 16 Oct. 55/2: Oh, please! Get a life!