My dd is going to be 13 at Christmas.
I've been scouring charity shops and Facebook marketplace. I bought a brand new Logo game for £1.99, a few dvds for 99p. I picked up a few arty bits from Olio (app where people give away things for free).
We have been given a TV, which is her birthday gift, then a family member who no longer uses their ps4 gave it to us, so we are wrapping that up with a few second hand games for Christmas.
So my advice, look out second hand or free to get the most for your money.
Shein is great for small gifts, stocking fillers, clothes and bits for their room. Ive ordered dd pin badges, a bag, fidget toys very cheaply.
Maybe follow the bargain thread on here, loads of bargains posted everyday.
If they are into art or cute things look up kawaii on ebay. Or I use blippo. Dd1 loves anything Japanese or anime.
Our other idea this year is to give small gifts relating to a day out the following year. So a bag of 2p coins and a postcard for a trip to the pier, some clay as a clue for a trip to madam tuessords, a sweetie pizza for a trip to their favourite pizza place. We are using clubcard vouchers for the big days out. Hoping to do a day out once a month and haven't decided on all of them yet but probably 1 theme park, a zoo, a castle, museum. We always take our own lunch so days out are relatively cheap.