There’s a ton of information online describing how to manage healthily on a $3 per day, per person food budget. Some use a somewhat smaller or slightly larger budget. As these are written for the secular world it obviously doesn’t account for kosher pricing or Shabbos but it may still be useful as a guide.
The main staples used are eggs, dry rice, dry beans, on-sale fresh produce, whole chickens, ground turkey, pasta and tomato sauce, and bulk spices.
It assumes you have a slow cooker, rice cooker, and reusable containers (for leftovers.)
It is recommended that you buy on sale, use coupons, shop different stores with lower prices and use leftovers.