In the US, there's an invaluable resource we use when figuring out a reasonable grocery budget. The US Department of Agriculture (USDA) puts out a monthly report at https://www.fns.usda.gov/cnpp/usda-food-plans-cost-food-reports-monthly-reports which gives details estimates of food costs per person by age, gender, and gradation of spend level (Thrifty through to Liberal). I'd highly recommend it.
We also put basic toiletries and household goods you could find at the grocery store in that budget line item and found it's still a reasonable estimation.
This is probably out of date, but as an example of what's available from the USDA website:
(Thrifty, and the numbers for Hawaii and Alaska, are in separate documents.)
