I think first you have to buy something substantial from The Good Guys (e.g. a TV, fridge, washing machine etc). They then invite you (via email or SMS) to activate reward categories. You then select and unlock the gift card category. Once you've unlocked the reward you can continue to purchase discounted gift cards for as long as you like.
You can also change your reward category once every 3 months.
There are over 100 gift cards available so I've pasted them all here: http://imgur.com/a/CxvYt
I spent $2500 on a purchase at the Good Guys in 2015 and never got any invite to a Concierge Rewards service. The site is very ambiguous as to how one obtains Concierge Rewards
Did you opt for extended warranty? Maybe that's the trigger.
No I didn't. Also bought a Galaxy S7 from TGG when they were released last year, with no extended warranty and no invite there either
It's an extra cost to join in conjunction with extended warranty. I bought $5K screen and was offered the service for another $400 odd. Didn't go with it. Details here: https://www.thegoodguys.com.au/concierge/concierge-rewards
Yep, definitely extended warranty. It's called concierge, best thing ever. Really offsets the cost of the extended warranty.
They have always been this way.