I usually manage to keep it to about $200 per week for DH, DS (1.5 year old) and I.
The biggest thing that helps me save money is the fact that I buy all my fruit, veg, meats & deli items from the local markets. I write a weekly meal plan before I go. I buy meat in bulk and divide it up into separate freezer bags once I get home. I buy fruit & veg that are in season hence cheaper and fresher.
I use microfiber cloths and make my own natural cleaning products.
I avoid supermarkets (hate Coles & Woolworths with a passion) but I do a small shop ($50) in Aldi once a week which includes nappies, chocolates, some dairy products, pasta & drinks.