We have 3 dcs, age 4, 9 and 11. I’ve probably spent between £200-£300 each, for a gift off us, santa and their stockings, but I don’t tend to add it up or equal it out, as long as they get the same number of gifts in their stocking and off santa.
I do try to go for quality over quantity, so their stocking items i tend to buy throughout the year when I see stuff they like. A reading book, dvd, notebook/ stationery, socks, torch, nail varnish, gadgets etc. Spreads the cost and I can usually buy decent stuff in sales (paper chase amazon etc.)
The main gift tends to be bought much closer to Christmas, managed to get good deals this year as they had a Fitbit kids / vtech watch off us, which were a good price around Black Friday.
Dd (9) tends to be the wildcard, as she asks for random stuff she’s seen on adverts near Christmas and it’s tricky separating out what she really wants against what’s a whim. Older ds is easy to budget for as it’s always new footy kit / astros. Younger ds has so far asked for one gift off santa.
I also get them all an eBay ‘preloved’ gift off us, which they love. Dd had a Lego friends set, which is discontinued (and was £100 when new!), ds1 has three footy tops (Barcelona, Real Madrid and PSG) and ds2 had a wooden train track tunnel bridge, which goes with all the track he inherited off ds1. All of them came to £65.