ALDI supermarkets are widely regarded as being cheap. http://www.aldi.com.au
Discounted egift cards some places in this list allow you to buy discounted gift cards for various supermarket retailers including Woolies and Coles. Category Choice Groceries gift card should work at all grocery stores.
Shopback supermarket gift card works at all grocery stores including Aldi.
There are occasional 10% discounts on IGA gift cards every few months.
NSW Seniors can get 5% off IGA gift cards all the time.
Check the current deals for the supermarkets. Coles Aldi Woolworths
Only buy the groceries that you need. Compare the prices in the catalogues if you have time.