Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This build is what I've been using in 3v3's since the first day Orianna was released.
This build utilizes Orianna's harassing capabilities by keeping opponents away by constantly using the Command: Attack and Command: Dissonance to bring down enemy HP, carry your lane, and keep your lane partner and team alive. Along with harassing, this build highlights Orianna's support factors with Command: Protect and Command: Dissonance to keep your enemies slowed and your teammates faster and alive.
With this build I prefer to lane with a champion with a AoE nuke, such as Nunu or Fiddlesticks, so I can use Command: Shockwave to keep the enemies within my partners blast radius.
If you have any recommendations or questions for/about this build, don't be afraid to contact me!