Are you shopping for yourself or for family/friends? I don't have to feed anyone else, so the groceries I buy are for myself only and as a rule, I try to grocery shop one day a week, same day each week. Sometimes I pop into the store now and then, although I'm trying to curb it because each time I go in, I buy something I wasn't planning to buy and it all adds up $$.
This morning I thought I would pay towards the upper end of my budget because once I lay everything out to be scanned, I had quite a bit of stuff! But it only cost about $30 (my weekly budget is $30-50). And I bought TONS of fruit, a good mix of vegetables, dairy, soy milk (=expensive), and bread I think.
There are certain items that cost VERY little: rice, beans, legumes, barley, buckwheat even. I find pasta more expensive but still good. Although vegetables are pricey, certain ones like cabbage, green beans, beets, carrots, squash (I think..), and others tend to be cheap. Like a whole head of cabbage is A LOT of cabbage, and it's less than $2 where I live. These make it easier to buy vegetables like peppers, tomatoes (which double or triple in price in the winter for me), cucumbers, mushrooms, different types of fruit, etc.
There are ways to balance it out I think and still manage to eat a variety of foods. I guess it all depends on what you were spending before, whether this is much more expensive for you, I can understand that
If you're looking to save a little money, some breakfast foods: cream of wheat, oat bran, oatmeal (original, not the flavour packs) tend to be REALLY cheap. The boxes of cream of wheat and oatbran that I buy have around 800 grams of cereal, and a serving of the cream of wheat is 3 tablespoons, so this stuff lasts a VERY long time and a box costs $2.99 here! I cook it with milk (you can cook it with water - though I don't recommend it myself) so the milk costs a little bit more, but I drink milk daily so it's something I would consume anyways. Cream of wheat has a lot of iron (I think it's enriched with iron) and I think both are good sources of fibre. They are filling and if you throw in fruits, nuts, spices (like cinnamon), you can get different tastes

They don't take very long to cook either, I'd say 5 minutes.