20% off in David Jones is usually not a good deal by itself but you can still get 10% off egift cards here (I bought mine with the paypal offer @ 20% off)
https://www.racq.com.au/membership/what-you-get/discounts/Da...
https://www.entertainmentbook.com.au/members/Gift-Cards
So stuff like RM Williams boots like these
https://www.davidjones.com/Product/20250138/Classic-Craftsma... comes to $436, comes to $392 with the egift cards and $382 if you couple with the amex vivid offer)
Other examples to use it on before egiftcard and amex discounts (ive only researched stuff that rarely goes on sale)
https://www.davidjones.com/shoes/mens-shoes/20668066/Houston... $559
https://www.davidjones.com/sale/men/shoes/21078899/Amsterdam... $559
https://www.davidjones.com/shoes/mens-shoes/20125533/Lausann... $399
https://www.davidjones.com/Product/21542171/Brigaderie-8cc-L... $219
https://www.davidjones.com/men/bags/21542176/Trainspotting-C... $599
A bit of work but good for those more expensive items. Enjoy!