Minimal effort recipes are also usually low cost.

Protein is normally the most expensive ingredient. For fish,my current bang for the buck/environment not so unkind choice is tinned mackerel which works out to about $10/kg. You can also get (uncooked) corned beef for $9-$11/kg, and other uncooked roasts at ~$10/kg. These will all last you multiple meals. That's how you save money. Buy and cook multiple meals at once. For many pasta and rice dishes, I cook at least twice what I need. One goes in our belly, the other goes in the fridge or freezer and can be reheated or microwaved for next to nothing.

For dessert, I'd go for baby yoghurt pouch for $0.75c. Go wild and add an apple or banana for another $0.68-$0.72c. Total $1.47. Again, cheaper if you bought in bulk, eg 1kg vanilla yoghurt $4 and 410g canned fruit salad $2.50.