a few more crystals to help enhance psychic abilities and medium ship are:
amethysts
tigers eye, (activates your 3rd eye)
pearls. (i've not much experience with pearls, but I have been told they are great aides to developing your psychic awareness.
moonstones
apatite
Coral
Labradorite
Obsidian
Opals
Black Onyx
Rock Crystals are supposedly very good with communicating with spirits
Amber
Ruby for dream guidance
Seraphinite is suppose to be the "Medium" stone.
as for herbs:
sage and sandalwood are good for cleansing the area. but, burning sage is rather smelly--you may want to stick with the sandalwood.
sandalwood is also good to enhance your visions, as is frankincense.
also for me--if I drink a cup of chamomile tea, it relaxes me to the point that I am able to have better luck with divining. also, I like to set my crystal balls around me. some are clear, and some are cloudy--but they seem to help me. I cannot always scry easily--but sit them around me when I meditate and I seem to do better with psychic and medium abilities.