A) You don't (and shouldn't!!) have to spend your own money on decorations for your class!! Mine make them...we made paper chains and cardboard tree hangings. I totally refused to spend money on this. So that one is on you! Doesn't matter what 'other' classes look like...some at my school look like Santa's Grotto with huge amounts of shop bought decorations. I don't have that kind of money (and even if I did I wouldn't spend it on school!)
B) You don't (and shouldn't!) have to buy gifts for your class. Again... forget what others do...it doesn't matter! I've made mine a lovely personalised bookmark in Canva, sprinkled a bit of 'festive glitter' over it and laminated. Cost nothing 🤷♀️
Don't be pressured by the 'it's for the children' bridade (SLT!!). If they insist on 'posh' decorations then they'll need to provide them.
At a previous school, my head decided we all had to stay late after school the last Friday in November to 'make our classrooms festive 'for the children' with trees, wreaths and full on decorations. Everyone privately complained and wondered where we were going to get these things from, but ultimately most went out and spend many ££££s on stuff.
I turned up on the Friday and asked 'where do I get my tree and decorations?' Head just looked astonished that I had the nerve to ask...I just said that I thought the idea was that we were all getting some lovely decorations for our room...I don't have any 🤷♀️ And I went home.
Grow a thick skin and don't be afraid to say 'no, I'm not going to be doing that!'