As others, stockings (and any big presents beside them) are from Santa and presents under the tree are labelled from whoever sent them.
stocking are generally small things that DCs will enjoy, will distract them in the morning, maybe a treat to give you time to organise breakfast, nice versions of everyday things or things Mum or Dad would never buy for DCs.
I tended to go by the rhyme:
something you want
something you need
something to eat and
something to read
So always a book and a mix of lovely fruit and some sweets (the fruit in our stockings when I was growing up was such a treat to have maybe 3 pieces, all to yourself, to enjoy when you wanted to…we didn’t have a lot of fruit and very little choice).
I also tended to put practical things like a new toothbrush, maybe some fancier hair bobbins than normal, some new bibs or bottle teats when small, a nice pencil for school etc as the needs. Maybe a travel sized version of regular toiletries.
And wants would be some small toy, a pack of cards for the set they are collecting, a new piece for the toy kitchen/shop/toolbox/car set…big thing they play with, that sort of thing. (Like a new piece of play food or a teapot or an extra car …to add to existing things).
All small. Mostly relatively cheap. Often involves things that get used up and need replacing from time to time. Or unusual things you don’t normally find (maybe from travels, or good shopping/researching) or don’t normally allow (some years, the mini boxes of cereal have been found there…that I never buy in the supermarket).