In my immediate family (adults - my parents, siblings, in-laws) we spend about £50 each for birthdays and the same for Christmas.
For my kids, I don't set a budget but keep it low - probably averaging about £50 as well for birthdays and Christmas, but some years more, e.g. a Yoto mini last year was about £70, plus stocking and a couple of Yoto cards was nearer £100 for that child, but the youngest needed nothing and was completely unaware so was probably more like £15! This year, I've got an Alexa device in an Amazon sale as the eldest's main present for £26, plus a few stocking fillers for about £15, so £40ish but they'll be delighted. The youngest is getting a toy that would normally be £30 but was £9 on Ebay, plus stocking fillers of about £10, so I'm totalling about £60 for two kids this year.
Partly this is because we try to be quite minimalist, tidy, and not have an overwhelming amount of stuff, they have loads already, and extended family go nuts (despite begging them to tone it down) and DC end up drowning in toys, many of which they lose interest in after 5 seconds.
I appreciate I'll need to spend more as they get older, but right now we shop second hand for most things and only buy things they'll love or need, rather than stuff that's exciting for a day.