Last year, I made my own as my daughters a the year before had Lego and they do not like chocolates much.
So made 24 little bags and used pen markers and wrote dates on the front.
Inside, I filled them with little things like pens, highlighters, tippex, pritt stick, Sellotape, plasters, hair accessories, mini torches, pencil case, staplers, small boxes of paper clips, mini notebooks, erasers, sharpeners, lipbalms, packs of tissues, hand warmers, bookmarks, miniature handcream, mini nail scissors, nail files, etc.
They really looked forward opening their advent bags every day. Made them finished their breakfast first. Used wrapping paper to make the bags so bags were different shape and size, selotaped them all round then dated them and hang them up on a line indoors with mini gold and silver pegs.
Got loads from Wilkinsons and the pound shop. Spent more in all than 2 boxes of Lego advent, I think around £60 but all those things were very useful and they still have loads left so am stuck this year with stocking fillers.