This is an original gown from the early Regency, accented with a delicate tulle overlay and featuring slim sleeves. I believe the original garment is in the Kyoto Museum collection. *Would need different sleeves.
Make your own Regency Gown.Pattern and Instructions. For the skirt I think I'd wear a circle skirt (I think this is just the instructions, but they're detailed enough to help with any pattern of this general type!