None of the above.
If you have adequate perlite in your mix, you don't need a layer of anything at the bottom. That's just another myth/good idea that isn't called for. A real PITA if you recycle your soil also.
You could try it if you want, really won't hurt anything and then you could see for yourself. The real small particles of peat and stuff migrate down and fill up all the space between the rocks and negate what you were trying to do in the first place.
But, nothing teaches like experience.
Wet