Christmas Eve box: we use the same box, dd stocking, copy of 'Twas the night before Xmas, snowman hot water bottle and Santa plastic plate and glass that have been used for many years. (Plate and glass were bought, along with a bowl and mug, as a seasonal spare set of crockery for toddler dd, probably cost €25 for all at the time, and we still keep all 4 with Christmas decorations for Christmas Eve and also any visiting small DCs over the season).
New items annually are pjs for DH, dd and I, lush bath bombs for dd and I, hot choc for everyone and a Christmas craft ale for DH. All of which I would buy anyway in. Winter/for Christmas. And it has always been a ritual rather than surprise in our house, with dd always knowing that it's me who does it (she bought DH pjs one year from her own money in a sale, and still wants it to appear despite being mid-teen).
We never did an Elf.
But we did do an advent calendar with pockets to fill for years (it didn't appear last year - I might hang it even just as decoration this year). I always had small chocs for the pockets (nets of Santa's/snowmen from M&S or Aldi generally, except the year toddler dd found the stash and I needed to buy matching soldiers from a deli for the final week as no small things left in stores!) and a slightly larger one for 124th.
Some days, i had a small present in there instead, Lego figures or tiny kits, or other "party bag" type bits. Or a free printable colouring/activity sheet printed from the internet and rolled up. Sometimes it was a note about an activity we'd do later that day, or a treasure hunt clue to send dd chasing around the house for the little present - about 4-5 clues was sufficient but she loved those!
. But I kept a long list of ideas to do in advent that I could cull for the calendar.
Very occasionally, I would set up her teddies/dolls in her room for when she'd wake up or get ho,e from school, that they were having a tea party, biggest teddy was reading story time to the rest, or some mischief was afoot - similar to EOTS activities but just her own toys and not something every day, maybe 2/3 times in December.