The biggest barrier to starting is getting equipped. You need to be very particular about this.
Any good unit portrays itself authentically.
They pay particular attention to this aspect. Since the Civil War was a volunteer army, there was variation from regiment to regiment. So, the equipment and uniform for one unit could be completely wrong for another unit. But, before you start buying, you need to choose an organization you wish to join. You need to choose what regiment you wish to portray.