The amount of Food Stamp dollars a family receives each month is dependent upon a formula including how much the family earns in income and where they live, since the cost of living varies from place to place. It is usually about $525 per month for a family of four. In any case, stretching those benefits to feed a family for 30 days is a challenge, especially as such benefits are reduced over time and by budget cuts.
There are some tricks and tips one can use to achieve that goal, however:
1) Buy fresh produce, in season - food isn't necessarily expensive, but processed food is much more so than crops grown and sold in stores without packaging. Buying potatoes, grapes, apples, etc. in the fall can be an inexpensive way to feed a family on food stamps and you are buying healthier food as well.
2) Buy in bulk - Many stores allow you to buy rice, oatmeal, and other staples in bulk out of barrels, so that you are only using a plastic bag and no other packaging. It is always cheaper to do this.
3) Buy real food - Kids like soda, sure, but it has almost no nutritional value. Buying fruit juice is better for them, that is, you would actually be feeding the family instead of just having something for them to drink.