Selenite is great!!! It actually amplifies the effects of other crystals. Selenite comes in a flat sheetobject with a 'grain' that goes in one direction, like a bunch of little lines. It conducts light in a linear fashion. You can place your dreaming stones in a mandala or geometric polygon on the sheet of selenite and program it and it will amplify it.
I slept with a chunk of selenite under my pillow, unfortunately it was too big and bulky and oncomfortable. But as an amplifier under your bed, it works great.
Herkimer diamond!!! For lucidity. But don't wear it during the day, too spacey.