I buy for:
my husband (something he wants & uses like tools and a silly thing from each kid and dog (e.g. chocolate, a fun print for the house, pyjamas)
our 3 children (he also buys stuff for them - he'll get the main presents, I try to do "something you want, something you need, something to wear, something to read"
my 6 nephews (usually keep it very simple e.g. a book each)
my parents (usually something silly they need like a colander or slippers with either tickets for a show or sometimes a posh bottle of spirits each and a photo in a frame of the dogs or kids)
my grandparents (I am lucky to have one of each side left but they don't need more stuff in their lives so I get them something they need or want with some guidance from my mum or aunt on the best type of socks or favourite biscuits)
a secret santa for one of my siblings or siblings in law - I'm one of 4 and we started doing this last year - it's a budget of £50 so can get something nice, I love how much time it's saved and it's much cheaper.
dogs (our 2, my mum & dad's 1, my siblings' 3) - usually a toy for ours and a snack for the others, it's just for something to unwrap
my mum does stockings for the kids (her decision - I'm not arguing!) and I do them for me and my husband (basics from Asda like: undies, a pack of coffee sachets or tea bags, a diary, toiletries, toothbrush, boozy tins)
my husband usually gets his mum's present but some years I've got it but because I work in theatre so can book the tickets easily, it's always his idea and choice
he used to put money in cards for all his nieces and nephews and never gave anything to his siblings (he's one 7, it's the norm in his family, they don't really do gifts) but that's on him, he'd rather treat his mum. I write Christmas cards for all his family.
My rule this year has been "don't over complicate it" - I am delighted with a book as a gift so I'm happy to give a book as a gift. I avoid giving just "stuff", it has to be a consumable or something that will be used or experienced. I try to buy local and/or independent where I can, especially with art prints and jewellery, or with theatre/gig tickets and restaurant vouchers.
My kids are all in high school now so don't get teacher presents but put a few quality streets in with a Christmas card for e.g. trumpet teacher or gym coach. I can't afford to be spending lots on that sort of thing so it's about the gesture.
It all sounds like quite a lot written down! I keep a spreadsheet(!) so I can keep tabs on who's got what and keep a running tally of the cost.