I spend €100 a week on 2 adults and 2 dogs. I shop at Tesco online, and take advantage of their '3 for €10' offers on fish/meat and cheese. Once I've decided on enough main ingredients for the week (usually 2 x the €10 meat/fish offers), I add the stuff to make the planned meals. Then I'll add a chicken or a joint of meat for the Sunday roast, plus any more vegetables we need. I don't buy bread, because it always goes off before we use it, instead I buy Tesco bread mixes (under €1 each) and make a loaf, or some rolls, usually once a week. Neither of us eat breakfast - DH grabs a sandwich for brunch on his way to work, I make some kind of lentil dish (tarka dal etc.) that lasts me a couple of days. I buy Tesco's own teabags and Nescafe instant coffee when it's on offer. DH will pick up a pint of milk every other day on his way home. (If there's any wriggle room left in the €100 budget when I've finished shopping for the main meals, I'll buy store-cupboard items (rice, pasta, tinned pie fillings, tinned tomatoes etc.) to bring us up to the limit. From September onwards, we'll be spending €120 a week, but €20 of that will be items for Christmas, one week a bottle of spirits, or a couple of decent wines, frozen pastry, jarred mincemeat - that sort of thing, so there's no massive spend to be done in December.
We eat really well using this method - granted there are only 2 of us, and no kids - but we're both omnivores (though I'm trying to reduce our meat intake for environmental reasons) and I love to cook and eat good food. I rarely buy anything processed, other than cheese and sometimes bacon, and cook from scratch 'cos then I know what's in what I'm eating! We don't snack, and nowadays we rarely drink alcohol either (gawd, that sounds worthy and boring, but it's not meant that way!) - it helps to keep the costs down. If I'm making something like bolognese sauce, or chilli, I usually make enough for a couple of meals (at least) and freeze the extra portions.
This week our dinners have been spicy sausage rolls (homemade), chicken biryani, chicken tikka masala, smoked salmon quiche (homemade) with new potatoes and salad, sausage, egg and chips, and spiced baked salmon with salad. Today will be shallow fried fish, chips and mushy peas. Brunch every day (for me) has been either tarka dal or chana dal, and a small yoghurt.
Every so often we'll put in a fresh fish order to be delivered and splash out (no pun intended) on 'posh' seafood like halibut, scallops, monkfish etc. - probably about €50 every two or three months. We have a large freezer!