Melbourne

OK, this is quite a severe exercise in budgeting. $50 doesn't go far. I think I'd do something like :

1. Ten bux for pantry items - oil, sauces, spices to refill stocks on hand - assuming rolled oats for breakfast cereal - sugar and chocolate goes in this category as does pasta and rice. Aldi as they are cheapest at the moment for pantry staples.
2. Ten bux for veg from market - should be able to get spuds, a couple of onions, pumpkin & leafy greens & maybe 1-2 capsicums.
3. Ten bux for fruit - apples etc from the cheaper end of the range. Bananas too as lots of nutrition for the price - also market - any money not spent in this category goes on 4) below.
4. Ten bux for non-meat protein like beans, cheese, mushrooms etc. Market or Aldi
5. Ten bux for meat - probably chicken and/or sausages plus eggs - Market or Aldi

This is a very rough estimate, and assumes that you'll be choosing from the cheaper end of supply - like home brand or on special or bagged veg for quick sale/use. I have omitted milk deliberately, as I don't know if you are a cow juice or nut/bean juice person or even a coffee/tea person. Add $10 for longlife bricks if you want to include milk of whatever sort, plus tea/coffee to make yourself, plus bread. Fair spread of nutrition over 5-7 days for one person. Not ideal but survivable for a while.