ExDH and I have always used the want/need/wear/read "rules" as a guideline for our present buying for DD so that we can:
a) make sure we don't go overboard buying loads of tat for the sake of it. It is so easy to buy lots and lots of little things for them to open on Christmas Day that never sees the light of day again until it gets sent to the charity shop because it is never used or binned because it was broken on the first use.
b) make sure there's a variety of things for her to open - yes if DD wanted 24 Lego sets we'd get her a few but I also think it's good to ensure she doesn't only get toys for Christmas/birthdays but also gets other presents like clothes/experiences/books and can see them as presents too. It's so sad to see so many people deride the "wear/read" part because clothes and books aren't "real" presents.
As a bookworm child, I would have loved nothing more than to just get a massive pile of books on Christmas day and I would have been over the moon so now whenever I'm buying presents for children I always automatically buy them a book and something else. Likewise with clothes - I will always buy DD any clothes she needs but anything that is OTT or expensive has always been, and will always be, a present. So I will happily buy her a new coat if she needs it but it will be practical and within my budget ... If she wants the entirely unpractical neon pink fluffy dry clean only jacket that she will be able to wear maybe the 10 days a year that are chilly enough to wear it but not wet enough to get ruined (we live in the NW where it's rainy 90% of the year) then it will be a Christmas/birthday gift.
c) be more conscious of the things we buy - quality over quantity and all that. I could easily just buy loads and loads of things here and there and buy far too much but instead we buy her a few well thought out things following the want/need/wear/read system and then family buy her whatever they want. As ExDH and I are separated she gets gifts from both of us plus both our extended families - my side is massive so lots of gifts even at just one from everyone whereas DHs is small but she's the only child so family spoil her rotten by buying multiple gifts. We would never tell family to stop buying her stuff so we just limit what we buy her to keep it at manageable levels.
d) budgeting - I use the want/need/wear/read system and structure my budget so I'm roughly spending equally per "rule" so theres a nice balance of gifts. Some years it might mean DD gets one big Lego set as a want but a set of a series of 5 books as her read as they are weighted equally in the budget; the following year she might get lots of little art things (pencils/pens/paints/pencil case/sketchbook etc) as her want and one fancy, hardback illustrated copy of a favourite book as her read; the year after she might get a day out somewhere as her want and a Kindle as her read etc ... the categories are fixed but the quantity/budget is flexible.
e) setting expectations - I want DD to appreciate the gifts she is given and if she just gets a massive pile of stuff then it is overwhelming and I don't think it's appreciated the same as receiving a few carefully thought out presents. Whether she gets 10 presents or 100 presents I want DD to be grateful that she received presents not turn into Dudley Dursley because she only got 36 presents this year but she had 38 last year.
It's easy when they're little to make present piles look impressive as presents tend to be cheaper but bigger but as they get older the presents get smaller but more expensive so I want DD to appreciate the gift she has not the size of the pile. For example I have spent £60 on my baby niece. I bought a jumparoo, a couple of big board books, a teddy and a Christmas dress and it's a big pile of stuff; I spent £60 on my teen nephew. It consists of a PlayStation game he wants, a graphic novel from his favourite series, the traditional lynx gift set and a beanie hat from his favourite football team ... Both sets of gifts follow the want/need/wear/read but one is a massive pile of stuff and the other all fits in a medium sized gift bag with room to spare for some chocolate/sweets but I've spent equitably on them both.