'Food, toiletries, washing powder, cleaning stuff, clothes, transport.'
I used to walk up to 5 miles each way rather than getting the bus when I was totally broke.
That is not ideal though.
Toiletries/cleaning stuff/washing powder - the cheapest non-bio powder from Aldi or lidl, same for everything else, but hot water and a rag gets a lot of dirt shifted. I tended to forego everything but £1 shampoo and conditioner and cheap soap for handwashing.
Everything was from the budget range. If something was inedible I would try it from somewhere else eg asda budget tortilla chips are good but aldi are too salty.
Clothes - as I say, from freebay/freecycle/cheap second hand shops but I didn't buy them often. If you absolutely need to due to weight change, try posting a message in a local freebay fb group.
Food - stick to cheap recipes - baked potatoes and cheese / shakshuka/ chickpea curry/lentil curry/ potato and carrot curry etc etc.
It's hard when you're exhausted but some things come together quite quickly.
Bread from Tesco or aldi is about 36p.
Cheap cereal from aldi.
Milk is 2 big bottles for £2 from farm foods if you're likely to get through it over the week.
I check discount shops for cheap food bargains but usually supermarkets are cheaper for staples - tins of tomato, chickpeas, kidney beans etc. And 20p spaghetti and 59p pesto from aldi is a fine meal. Pesto will last 3 or 4 meals.