I would focus on the dc’s presents and cut back on other things as much as possible.
Are the adults in your life reasonable about getting no gift or a token gift? Grandparents might enjoy homemade biscuits in a hand crafted box. And that doubles as two craft activities before Christmas.
If you normally do expensive outings you could substitute a school fair for a posh craft fair, or support the local drama group rather than go to a pantomime. Eat a meal before you go out and pack a treat and some drinks to save ££
There’s also lots of free things you can make an event of - like a walk to forage for pinecones, a drive to see Christmas lights, or a trip to a scenic spot to watch a sunrise or sunset with a flask of hot chocolate.
There is no limit to what you can spend on Christmas dinner, but you can also do very well on a budget. Aldi were selling carrots, Brussels sprouts and melons for 29c on Christmas Eve. A small turkey will save you the hassle of doing interesting things with the leftovers! A gingerbread house costs a fraction of the price of a Christmas cake and is another activity for the dc. Find out what your family really like about Christmas dinner and cut back on everything else!
I would advise caution about the bargain threads because if you don’t have nerves of steel you could end up spending more than you planned or get caught up in a craze and have to find space for a giant unicorn named Robert But if you have the self control for it there are great bargains!
I used to tell my dc that the sooner they wrote to santa the better the chance of getting what they wanted. I wasn’t quite that blunt, there was a lovely story involved, but it gave me a chance to bargain hunt and leverage when they would try and change their minds! Smyths usually have a sale around mid September with about 20% off although it varies and obviously there’s no guarantee.
Other posters have mentioned camel camel.com that allows you to create a wishlist and it will send an alert when the price drops. It also shows price fluctuations for the last few months so you can judge if something is a good price or not before buying. If you’re looking at LEGO sets, brickset is a great website and shows prices across the different European amazons. It’s worth checking out other amazons for big items. And if you sign up with a cash back site you can get money back for online shopping which also helps.
I’d try and focus on one biggish gift that they really want (if you can) and a small amount on other small gifts. Wrap everything as that makes more impact. AliExpress have lovely stationery for pennies if you don’t mind waiting months for free shipping (search for Kawaii).
If you do stockings bulk them out with a comic or bag of popcorn or a tube of Pringles. Does Santa come? My childhood Christmases were magical even though we had very little. The sitting room always looked as if a very overweight and slightly drunk man had come down the chimney. The grate was knocked over, furniture out of place, soot on the hearth, coal scattered, ornaments brushed off the tree! There were sooty marks on our presents too. And he always left something behind that we would leave out for him the next year like a handkerchief or a button. I vividly remember the year we found a scarlet thread snagged on the corner of a brick on our 1970s fireplace.
I’m not suggesting you go overboard but you can get a massive impact from one small detail!
I’ve had a fair few tight christmasses both as a child and as an adult and they’ve been absolutely magical.