There was a lovely thread last year (goodness, have I been on Gransnet that long already?) on the same subject with lots of links and good ideas.
The internet abounds with ideas, and I know I have loads of old magazines (especially from the 80s when the children were small) with ideas in, knitting and sewing patterns, recipes and so on.
If you want to go the whole hog, you are looking at:
Home made Christmas cards,
Home made presents (baked, sewn, knitted)
Home made wrapping paper (potato prints!)
Home made decorations
Home baked cakes, biscuits and sweets
And a Christmas dinner made from scratch with more imaginative home made decorations on the table.
It is a lot of work, and you are right to start now!