Edit: Missed your post clarifying the $100 per week versus $100 per month! So you can ignore that part!
Sounds like you're already doing a lot of things right, so I'm sure you'll be able to get the costs down by making some changes, but can I first say that I'm not sure your $100 per month goal for a family of 3.5 is realistic, even if one of the 3 is a toddler. Especially if that includes cleaning supplies, booze, pet food, etc! As a comparison, the article below talks about $1.75 (Canadian) per day, or $52.50 per 30 day month, as the extreme poverty line level of food costs.
http://globalnews.ca/news/1954331/cooking-and-eating-on-1-75-a-day-as-b-c-residents-take-on-challenge-to-end-poverty/?hootPostID=a542bce47f150dc29c773490f935fe8aThat being said, I think there are a few basic approaches to reducing food costs, and of course, you get most impact by combining them.
1. Reduce waste - make sure that everything gets eaten and nothing goes to waste. Chop up broccoli stalks finely so you aren't just using the crowns, eat the radish greens and not just the radishes (can cook them like spinach and other greens) and so on. For meat eaters this would means using bones to make stock. Eke every bit of nutrition from what you buy, and wring every calorie from the food too. Rotate stock so nothing expires, and freeze things right after making them if you think they won't get eaten in time.
2. Eat down your stockpile. Assess what's in your cupboards and make a point of using the stuff that's been there for a while. This might seem like it would only save you money in the short term (and it does - so save that money and use it to pay down debt, which saves you interest, or get it invested, so that it starts earning you interest sooner!) But it also helps you see the kind of stuff you buy and never use. Weird ingredients, large quantities of spices that you might only use once for a specific recipe, and so on. Over time, this may help you learn what
not to buy. An example - I am not the usual cake baker in my extended family. But twice in the last 10 or so years, I've wanted to make a special cake for someone, and that left me with half a bag of icing sugar in my cupboard for years. It's not bad/spoiled but it won't realistically get used for its intended purpose. So I've mixed it in with regular white sugar to use in my tea and coffee (short term saving). Long term? I probably would plan to make something different, or borrow a bit of icing sugar from my mom next time (she's the usual cake baker).
3. Choose cheaper alternatives. This is where you switch from fake meat to plain tofu, from canned to dry beans (hint: lentils and split peas don't need pre-soaking or long cooking, if that's an issue), from mangos to apples, etc. Figure out what's cheapest by serving size - rice (white or brown), pasta, other grains like bulgar wheat, couscous, barley, etc, and make that more often and the more expensive stuff less often.
4. Shop sales - shop at discount grocery stores, plan meals around loss leaders, use coupons where you can, price match where available, etc
You'll get tons of ideas over in the "Throw Down the Gauntlet" section of the forum, if you haven't looked there yet. Here are some of the more recent threads:
http://forum.mrmoneymustache.com/throw-down-the-gauntlet/eat-all-the-food-in-your-house-take-2/ http://forum.mrmoneymustache.com/throw-down-the-gauntlet/fire-drill!-skip-this-week's-grocery-shop/ http://forum.mrmoneymustache.com/throw-down-the-gauntlet/food-waste-throw-down!/ http://forum.mrmoneymustache.com/throw-down-the-gauntlet/snap-or-$5day-healthy-eating-challenge/ http://forum.mrmoneymustache.com/throw-down-the-gauntlet/stick-to-a-grocery-budget-in-2015-challenge/ Also, on the subject of tracking grocery spending:
(recent)
http://forum.mrmoneymustache.com/throw-down-the-gauntlet/track-and-categorize-all-grocery-spending-for-march-2015!/ (original thread that inspired the new one)
http://forum.mrmoneymustache.com/throw-down-the-gauntlet/track-and-categorize-grocery-spending-all-march!/msg230366/ Full disclosure: I have not ever tracked and categorized my grocery spending as per these threads. I can imagine it would be helpful to do. I can also imagine not having the time or energy to do it with a newborn! So if that idea is too daunting, consider just finding out how much of your budget is groceries and how much cleaning and pet supplies. If you have one small dog, are a slob, and each of you has one beer on Friday night, that would be very different from having two big dogs, being a neat freak and having a couple of drinks each night. If the latter is the case, then you might not be as far off in your
grocery budget as you think!
By the way, you don't have to sit with receipt and calculator to get some idea of how much is going to food. Just get the cashier to ring in two separate transactions. Put all the food on the belt first, total, and pay. Then ring through everything else. Voila! You know your grocery costs, and also how much you're paying for pets, booze, and cleaning. Extra benefit - you can cut costs in those areas too - I recommend dropping the cleaning first ;-)