Good advice above. Making your own food is essential to saving money on food. It doesn't have to be complicated unless you want it to be and enjoy that sort of thing. Some of the best cuisine in the world is just very simple stuff made with exceptionally good ingredients.
Try to center your meals on cheap things like grains, beans, and whatever produce is in season. Then if you want to add something more expensive as a treat, it will be offset by the cheaper things.
Grow your own herbs and try a few other simple foods like tomatoes. I'm in the US, but I assume these things are also expensive in stores in Australia ($3 for a handful of basil?!), and growing your own can shave off a fair amount of your grocery bill. Even if you just have a windowsill or a patio, you can grow a few things in small pots.
Use up every last bit of the food you buy (or grow). Almost anything can be frozen or turned into something that freezes well. If you don't like leftovers, save it in the freezer for 2 weeks and it will feel like convenience food rather than "Ugh, I just ate that for the past 4 days in a row!"
I spend about $300/month on groceries.