I don't have any suggestions for gluten or dairy-free, sorry. What I've got is just run-of-the-mill budgeting stuff that I do.
1. I write a menu plan for the week before I go shopping. I make a list, and I try not to deviate from it (unless I go shopping hungry, and then I am weak, weak, weak) I know how much my family eats, and how much most of the recipes I use make, and so at least half of my meal slots read "leftovers". When I make out the menu plan, I look at what I've already got that needs used up: veggies getting wilty, leftovers, partial packages of tortillas, etc, and put in meals using up those ingredients in the first couple of days. Toward the end of the week, when fresh produce is used up or getting old, I plan a couple of meals that are based off of pantry staples or things I've got in the freezer, so that if things don't go according to plan (and they never do - someone invites us over to eat, leftovers last longer than I thought they would) that meal can be bumped into the next week without any perishable foods being wasted.
2. I shop one time for the whole week. This saves on gas money, too.
3. Crock pot cooking - If I see a really cheap cut of meat, I buy it and take it home, and then I freeze it. I look for a recipe and work it into the next weeks meal plan. I don't have a deep freeze, unfortunately, so I can't really stock up huge amounts.
I don't really do couponing - I find that most coupons aren't for things I use anyway, or generic brands are still cheaper. I do keep an eye on the sales flyers and I also have a general idea of which local stores always have the best prices on things like meat, milk, etc (and it is hardly ever Wal-Mart). I get rice in huge bags at the asian store.