I'm with the previous poster. We spend $50 on groceries every week. No chips, no soda, no processed foods. Everything is green or a fruit or ... tofu.
I am not employed, so we're living on one income. Every Saturday, we go to the walmart supercenter and Costco. We get great deals on fruits at costco and we're both major fruit eaters. The Costco membership pays for itself in a year, but it's not absolutely required to save money. At Walmart, we get bell peppers, potatoes, onions, mushrooms, green onions, tomatoes (in season), baby carrots, plain NF yogurt, part-skim mozzarella cheese (some weeks), 1 doz eggs, 1/2 gal skim milk, bananas and maybe a pomegranate or two. We also get our frozen veggies here as well. Granted, different parts of the US have different price ranges for the same foods. I would put most of your grocery bill into frozen foods. You can buy in bulk (saving some money).
Another way to decrease spending is to cook your own food. I cook for my hubby and myself and I have made a wide variety of dishes so we have at least 4-5 dishes throughout the week. That's about a new dish everyday, which means we don't get bored easily. We eat out once a week because I want a break and so does hubby.
Everyone's budget is different. You might end up combining some of the ideas mentioned here to make your own plan. It is a process of trial and error. I used to buy veggies neither my hubby or I liked and it would end up going to waste. So now, I really think about what I'm going to make during the week before I buy. Basically, I have a weekly plan for food.
Good luck - it is frustrating but you do get the hang of it eventually.