A small tree, real or not, won't break the bank. You can also make some ornaments on your own. String popcorn or cranberries. Bake cookies on a string or create snowflakes out of paper. A family I know makes a new menorah every year as a family activity.
Cookies make the whole house smell like the holidays.
You can get creative and make little gingerbread men and stars or go for chocolate chip. You can bake from scratch or find a mix or use the slice and bake kind if, like me, you were born without the baking gene. Build a snowman. Get out into the cold air. Watch your breath.