There are precious few occasions when you’re not only allowed but encouraged to go absolutely all-out in what you’re wearing: Halloween, your own birthday, and the month of December (and first day of January). So take advantage of it, and wear multiple kinds of sparkle. Try a flashy, short sequin dress with some sparkly platform heels.
Balance out all that sparkle with a top knot — a bun that looks like you’ve just clipped your hair to the top of your head, and let it do its thing. A green coat is also festive, but not too much so. And you have the choice to put your arms through the sleeves of your jacket, or not. In the fashion world, that’s always optional.