How much do you spend on groceries/household items in a month?

Well, it doesn't really matter what other people spend on this. What matters is what you need to spend. The cost of living can be VERY different from one city to the next or one state to the next.

The best way to make a budget is to start by simply tracking what you actually spend for a month or two. Write it all down, or get a software program (e.g. Quicken Basic) that will help you track your spending.

Once you know what you actually spend, you can start looking at whether you can decrease that at all with some simple brand switching (for example, can you save money by buying generic instead of brand name canned and packaged products?). Then you can look at whether you can decrease it more by making simple changes (for example, if you buy pre-packaged salad mix, can you save money by purchasing the ingredients separately instead and cutting up the veggies yourself?). Then you can look at whether you can decrease it more by making some simple switches (for example, if you enjoy snack foods like chips & dip, could you make the dip yourself rather than buying it already made, or for even more savings, could you switch to something really inexpensive like popcorn that you pop yourself (not the kind that comes in a microwave bag) instead? Can you save more by clipping coupons (some people have the patience and discipline for this and others don't - so you need to know yourself too, and what kinds of changes you are likely to be able to sustain and what others you aren't). Can you switch from canned soda to 2-liter bottles of the same soda (much cheaper per ounce) and drink it out of a glass instead of out of a can? Could you switch from soda to KoolAde (much cheaper than soda)? Again - some of these changes you will find relatively simple to make, while others may be too much trouble, or will make you feel too grumpy or deprived (or stressed to spend extra time you don't have) so aren't worth it.

It also depends on how and what you eat. Some kinds of foods are definitely more expensive than others (for example beans-and-rice dishes can be as tasty and nutritious as steak & potatoes, but cost a lot less).

Creating a good budget and living frugally are "processes" that always need to keep being adjusted, not a one-time thing.

I (personally) think you could probably feed a family of 4 on $450 a month, but with 2 still in diapers (and diapers coming out of your grocery store budget) it could be fairly challenging. If you live in an area with a very high cost of living (thinking San Francisco or NYC) you might need to budget more than that for food.

For what its worth, I spend about $45/week to feed myself (one) but I have spent both more and less than that depending on what my finances could afford at the time.