I'm sure others who do similar have already replied, but our box is a mixture of new and old things and very much was designed around getting dd with SNs through a wind down routine to get a good sleep.
We use a cardboard box that held a gift years ago and stores our seasonal storybook and DVD collection the rest of the year.
When dd was very small, I got a 2nd plastic plate, bowl, glass set for her which was Christmas themed. She used it lots along with her version covered in flowers until she graduated to china plates - the flowers one was more heavily used and ready for recycling but we kept the Christmas one for taking out for about 6 weeks annually (1st Dec to 6th Jan when tree came down). Her plate and glass went into the box on 24th, to put out a glass of milk and some cookies we baked in the afternoon for Santa's snack.
Her stocking - used from her very first Christmas - was also in the box to lay out.
Our family edition of "'Twas the night before Christmas" as her bedtime story. (It didn't come out with the rest of the books on 1st Dec, but was kept for 24th).
And dd's hot water bottle with a snowman cover, used all winter, also got placed inside.
And then the consumables.
2 posh hot chocolate stirrers on sticks (for dd and I) and a craft Christmas beer for DH. And maybe a strange snack the he and dd would like (they love things like wasabi peas!).
A lush bath bomb each for DD and I, and a seasonal or otherwise nice treat shower gel for DH.
A pair of winter PJs for everyone, sometimes a pair of fluffy sock or slippers for dd - some years, some or all were Christmassy, but more often than not, just ordinary new PJs. Even if festive, they were worn all winter and often year round.
It only came out after dinner and after we lit the Christmas candle.
Dd would lay out her stocking and Santa's snack, before going up for a relaxing bath and get into new PJs. Come back down for a mug of hot chocolate to drink and her bedtime meds (a nightly thing anyway but normally powdered hot chocolate), before bring a cosy HWB up to hear the story in bed and settle down for a good sleep.
For us, it was a combination of necessary and nice things, but all things we reused over and over or things we would have gotten anyway, just all made more special by being packaged together. Rather than being a lot of "needless expense".