There are loads of things you can do to make Christmas exciting even without having any money.
You can still make a fuss over dinner (even if it ends up being your normal dinner)
You can make hats from old newspapers (or any scrap paper and felt tip pens), and you could make bunting from old paper too.
If you have no decorations, then you can make those too
In terms of presents, be imaginative with that too. Buy something from the charity shop - it's surprising what they have at this time of year. Or wrap up clothes you were going to buy anyway.
Stockings are a great way of doing christmas (you can make those too or just use cushion covers) - apple, orange, chocolate, nuts, book, socks.
Go to some church christmas services, especially candlelit or "dress up" crib services - they feel magical. (And you should be able to find one on christmas day too)
Another idea might be to go to your local food bank - they have shelves of "help yourself" which are meant to be items that aren't on the strict provisions list. Uf you speak to the supervisor in confidence they will probably let you pick a few treats.