Have a look online OP for things you can make for your DC for they're stockings.
This is for how to make your own crayons,you just take bits of broken crayons and you can melt them and make them into lovely shapes,hearts,stars ect by using some metal cookie cutters.
www.google.co.uk/?gws_rd=ssl#q=how+to+make+crayons
Homemade sweets,chocolates,toffee,fudge,truffles,toffee apples things like that can all usually be made for pennys.
www.google.co.uk/?gws_rd=ssl#q=how+to+make+sweets
Personalised Chocolate bars,we've done these before for party bags and they went down really really well and the other parents thought we'd spent a fortune buying them ready made,we didn't we did them ourselves.
We used bars of Asda Smartprice Chocolate(it tastes really good and comes in milk or dark)100g and it's only 30p a bar.
groceries.asda.com/product/chocolate-blocks/asda-smart-price-milk-chocolate/910002088611
If you look online there are loads and loads of free printable chocolate bar wrappers.Those bars of chocolate,the wrappers and a kids pritt stick(glue stick)was all we needed.With the paper and printing each bar cost us less than 35p and they're anywhere from £3 upwards to get them made by someone else.
If you don't have a printer you could ask a friend or family member to print the wrappers of for you.They look really good and all the children loved them and it took less than a minute to do each one.
If you have a printer or know someone that would print stuff of for you,you could also do some Christmas coloring pages,christmas dot to dots,Christmas puzzle sheets to go with the crayons.Roll the pages up and tie them with a red ribbon.
I agree about the playdough I'd take that back and if you still want to get your LO some playdough there are Playdough advent calendars out this year,they should be heavily reduced now or failing that 99p shops,poundland and The works all usually sell really good playdough sets for well under £5.