Choosing a costume for a party can be stressful if you leave it to the last minute, and even worse, you may end up with one you don't like, that doesn't work for you, and that can make having fun at the party difficult.
First thing you should do is consider what you will be doing at the party.
Will you be eating and drinking a lot? If so, a full face mask or covering will make it tough unless you remove it.
There are plenty of costumes that do not cover your face.
Then again, if you do not want to be recognized, that is a great way to go.
Will you be active at the party? Is range of motion an issue? If dancing, you want an outfit you can move around freely in.
Also, what will the temperature be like? Will it cool, or hot and crowded? Many costumes are quite warm which can be good or bad.
You don't want to be uncomfortable sweating all night long, and conversely, if it's cool, wearing a jacket over your costume may not quite cut it either.
Also consider what kind of costume makes sense for you.
What is in character and fun? I make a great Troll but a poor Fairy for example.
I think I'd make a great goat or superhero, but I'm not the donkey or villain type.
What works for you? There isn't ever an ideal costume, but several decent choices usually.
By considering the issues above you should be able to choose an excellent one!