If it’s a rectangle with a low ceiling, I’d go with carpet on the floors. And make bass traps to hang on the walls in the corners out of Rockwool 4" thick 2’x4’ panels. You can buy them pre-made or make your own, just put a frame around them and staple acoustic fabric.
And then a couple more wall treatmeants out of 2" think Owens Corning 703 compressed fiberglass. Same deal with wrapping with acetic fabric.
That’s if you want a nice DIY project!
Not necessary, but that will greatly improve the acoustics of the room.