Did this on myself last night. Self done 18g triple helix with 3mm and two 2.5mm black opal gems. Jewelry from Neometal.
Please note: I am a professional piercer, so self piercing is much different in my case than it is for most people. I absolutely do not condone attempting this by yourself, please seek out a reputable body piercer in your area. www.SafePiercing.org has a member locator which is a great place to start your search!