Family of 4 (2 under 4). We spend about $600 a month and that includes everything including 4 dinners out and for more pop than I care to admit (that's another question).
We shop at Sams for dipes, wipes, milk, and all things that we normally purchase that is in bulk. We do not buy/use many paper towels and only buy Scott tissue.
We shop at Walmart for everything else except meat. Our local IGA has had meat sales and I seriously stock up. I spent $60 for meat about 2 1/2 months ago. (pork chops, chicken breasts, chicken legs, sausage, hamburger, and roasts)
When I do buy something new from Sam's (like toilet paper, shampoo, conditioner, laundry detergent, etc).....I write the date on it with a sharpie of the date I opened it for the first time. This helps me keep a check on how quickly we really are going through it.
I have compared the prices of Sam's items to Walmarts and they are always cheaper....and Walmart is almost always cheaper item by item than anywhere else.
We also make most of our meals from scratch and freeze them to make them very convenient (I work 3 evenings a week). THis has saved us a ton of money and time - and no left overs. We make lasagnas and such in servings of 3 - one for each adult and one to share between the girls.
Good luck....I hope you find what you are looking for! :)