I’ve only attached “real ribbon” to a cake twice (once to fondant and once to butter cream) and I don’t know how most people do it, but since no on has responded yet, I thought I’d tell you how I did it and maybe that will give you some more ideas. I use little dabs of piping gel about every 6 inches. If your ribbon is a light color or not super thick, it will show through slightly. Now that’s around the bottom of a tier. If you did it in the middle, then you would probably have to use more so it wouldn’t sag, but again, depending on your ribbon, that will make any gel that soaks through the ribbon more noticeable. Hope that helps somehow!