Every year is different... but a LOT. Not like Dudly (from Harry Potter "Last year there were 37!") a lot, but a lot.
How I do it is like this:
1) I make a list of everything I WANT to get / NEED to get (sigh... 2 different lists)
2) I buy them
3) I divide them between Santa, Mom (special), Dad (special), and Mom+Dad (big things)
What's the "need'? Well... I save shopping for Xmas. New clothes, pillows, dishes.... any winter & spring sports/camps... any "memberships" (zoo, seasons passes)... electronics... those ALL get bought for xmas. Bdays are smallish (1 gift each), but xmas is probably 2/3s needed (would be buying ***anyway***) and 1/3 bonus (toy type/ treats)
There's no exact "number". It REALLY depends on the year. It's always exciting, though, because when you've been 2 inches grown out of your pants, and your snow jacket is too tight to be comfy (but still theoretically fits)... clothes ARE fun to get. When we haven't had a TV for 4 months... that's an exciting thing. We hold off on MOST things until xmas.
The "best" (aka most wished for; regardless of price) always get brought from Santa. Adds a little humility into the process!!!
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ADDED:
Did you know I have God Like Powers???
I do.
It all started because I have both Serbian and Albanian Friends. BOTH have Santa... and Santa NEVER comes on the 25th! The Orthodox Christians celebrate xmas on Jan 7th (9th? Oh... Dragana will shoot me for messing this up!), and the Albanian/Kosovars are MUSLIM. Santa comes to THOSE houses "When Dad gets paid" (as the norm). It's SUPER fun in their schools (the muslims), because Santa comes on all different nights... so you never know when you're going to wake up and find presents under the New Year's Tree OR when your friends will! Stockings hang up for weeks, and one night, Santa comes...
This gave me an idea a few years ago. I MOVED XMAS.
Only by a day in our house, but my God Like Powers know no bounds. I could move it by a week! Or a month!
I moved it, because with all the BIRTHDAYS we have on xmas, there's no way to avoid family on the 25th and have it just be out nuclear family. And, like your extended family, EVERYONE does xmas differently (I have a niece and nephew who don't get santa presents, either, but the other cousins do!) so it makes for a bit of friction. And it made for EXHAUSTION when we tried to have our "own" xmas in the morning and then went running around... and impossibility for our own traditions if we were all sleeping over.
Moving "xmas" / "when Santa comes" has been the BEST, hands down, decision I have ever made regarding holidays. Period. Even better than the insisting Uncle J wear clothes when we're all present. As Uncle J is neither a young man, nor a particularly fit man... this decision ranks rather high as well. Esp with the rest of the family who couldn't figure out a way to get him to do it (Uncle J has a weakness for Scotch. ONLY if I don't see his wrinkled behind for the entire day, do I give him a bottle of Glen Livet upon leaving. My mum prefers we leave last. I wonder why?