Brown bread (bread made with rolled oats and mollasses) and baked beans has been one of my goto cheap bulk meals since I was little kid

Ill try to remember to post the recipes when I get home from work.

Milk whipped into mashed potatoes also makes a barebones meal that covers essential nutrition. And it is the season where you can buy a large bag of potatoes for cheap. (Taste and fibre content can be improved if you throw in a can of corn nibblets as well)