We always shopped and cooked separately - some non-food stuff was shared and on a rota (e.g. washing up liquid, loo roll.) I sometimes cooked for my flatmates, but I was never that broke as a student (the first time round) and never made anything all that expensive... just for fun, really, and they couldn't afford to return the gesture.
If you want to take advantage of big value packs of meat, veg etc, you can get plastic or foil tubs from the pound shop and freeze things in individual portions. It means you only have to cook once or twice a week for decent quality food every night.
We usually went to the supermarket together and shared a taxi home, because it worked out to be no more expensive than the delivery charge for home delivery, and if you go at the end of the day you can find the discounted stuff.
At one point I had a housemate who was eating loads of my food - I offered once or twice, and she took that to mean she could always help herself, even when I said that I couldn't afford to keep feeding her. So I took to only cooking things she wouldn't eat (she was vegetarian.)
Perhaps see whether your flatmates like the same food as you and whether they can cook before you make a commitment, but you can probably make it work either way. It doesn't have to be all-or-nothing, you can eat together some nights and apart on others.