Celts are an awesome army to start out with. As said, they fought so many different people. You can make “generic” looking Celts to represent Britons, Gauls, Galatians, etc.
The other benefit is that so many armies hired Celts as well. So if you ever say want to start a Carthaginian army and you already have a ton of Celts, you’ve got a good chunk of your army already there.
