Well done op and congratulations on your brand new life. It will be hard but you will be on control.
I learnt a lot from mn when I was a newly single parent.
If you only shop in lidl aldi and farm foods. There's a lot of spending temptation in the big supermarkets.
Meal plan like there's no tomorrow. Try and monthly shop for dry goods if you can it keeps me away from the shops a bit more.
Make sure you're home is as insulated as possible. There are grants for loft insulation etc if you google.
Buy decent flask if you like hot drinks. Makes a cold park trip with a small child much more bearable and works so much better than a takeaway cup for keeping the coffee warm! Honestly well worth the money.
Never leave the house without drinks and snacks. My dds had the small sistema bottles for years which fit in the smallest handbag - that and a cereal bar at the minimum for any event of leaving the house. The cost difference between taking from a multipack and buying a snack out is huge.
Buy big and decant - make sure you have some small tubs which they often sell in lidl but they are everywhere - we have the Russian doll style lunch box tubs but anything will do. I buy in bulk own brand choc buttons for example.
Get yourself a lunch box as well as the kids.
Ditch brands as much as you can. The only thing I concur after 12 years that needs to be branded is mayonaise. Lidl own brand is 🤮. I even ditched green giant.
Sign up to some testing web sites. I got this off mn back and did sense reach. Worked better when the kids were babies but I got whole boxes of laundry capsules etc for just filling in the survey. I reckon I did quite well over the years in products.
Register with your local pharmacist then you can get things like calpol for you dc free. Adds up.
Get an electric blanket if you can - ask for one for Xmas maybe. Mine cost £12 in asda god best money ever spent I've had it years and really makes a huge difference being on only a few minutes.
Get used to reselling kids clothes. Baby clothes go quick on fb - much less faff that EBay.
I really had to learn the hard way to spread costs over the year. Now I'm a big wiser I have a few bank accounts on the go which I pay into each month for vet bills, kids activities and a weekend away one (this one is suffering just now!) to avoid big scary bill heart palpitations. Just realised I don't have one for the bastard car mot but you get the idea.