We eat mostly vegan (allergies and dd2 is vegetarian). So lots of beans, pulses, lentils. Most of our meals are potato or rice based as I have to eat gluten free aswell!
Lunches are often leftovers, or dds have sandwiches/couscous etc.
I dont buy prepackaged snacks for lunches, cheap big packs of biscuits or we make cakes/flapjacks.
I use frozen vegetables, cheaper than fresh usually.
I'm lucky we can access a community kitchen where you pay £4 a week and get a small food shop (a few tins, whatever fruit/veg/bread has been donated etc) I use olio for bread and some veg etc.
Cleaning stuff I use concentrate and dilute it which saves alot. I use wash powder which lasts ages. I bulk buy toilet roll and cat food on amazon.
Basically the biggest money saver is use everything before going food shopping. We have leftover soup about once a week, where any sad looking veg gets chucked in the slow cooker with some lentils which we have for lunches. If I use something like coconut milk, I will make sure there's another recipe to use up the rest so it doesn't get wasted. Manky bananas get made into banana bread, I cook slightly sad looking apples/pears to have on porridge or rice pudding.