Get creative for school dress up days, never buy costumes, borrow or improvise.
Walk or cycle when you can.
See if anyone has an old phone going spare, then get sim only, rolling monthly contracts.
Let friends know your happy to take older DC kids clothes when outgrown.
Price comparison every outgoing possible, usually the threat of cancelling gets you a cheaper price without actual having the faff of changing.
If you have a streaming service, do you really watch regular TV? Cancel TV licence if not.
Hang out washing, even on cold days it tends to dry.
Bath kids ever other day instead of every day.
Only wash clothes that are actually dirty.
Keep snack and drink in bag.
Meal plan and do 1 big shop a week, freeze milk and bread to last the week. Check price per grams rather than actual price to get the best value (usually right below the price on the ticket).
Make big basic old school traybakes (sub butter for marg). Cornflake cakes. Basic cookies (chop up a cheap choc bar instead of choc drops). Initial outlay is the same as buying them pre made but you get so many extra portions, more filling than shop bought.
Boiled eggs, pesto pasta, bread sticks and hummus, toast- filling snacks.
Cheap dinner- pasta bake, jacket potatoes, omelet, beans on toast, cheap pack noodles with handful of frozen veg, gnocchi, toad in the hole, homemade pizza.
Always keep some quick junk food in your freezer, if your having a bad day this may stop you getting a takeaway.
Fairy washing up liquid and decent hair conditioner are more cost effective than the cheaper alternatives, you use so much less.
Save up rewards or your small change- use for sweets and treats when having a day out.
Activities - movies for juniors (take own snacks), movie night at home, swimming, parks- different ones to keep it exciting, feeding ducks, garden centre or pet shop to look at animals (some allow you to feed fish for 50p), geocaching, library events, visit family, organise playdates or park visits with friends, have board game nights. Baking any of the above suggestions with DC, trip to beach/forest (watch out for expensive parking though). Keep a watch on local social media for free events. Loads of free activities/scavenger hunts and such to make walks more exciting and can be printed cheaply at the library.
Don't go to fates, markets, community days with paid for rides- they look cheap on the surface but it ends up leaving DC frustrated that they can't do and have everything there. Don't go to shops unless essential.
Use social media less, it just makes you feel crap/guilty/envious.