Orianna is one of the best champions in the game. Her Command: Shockwave can drastically change the flow of the battle because everyone caught in it is grouped for even more aoe damage that can be dealt by your team. Having said that, if you miss your Command: Shockwave, a huge portion of your possible damage is gone because the more people you pull in with your Command: Shockwave, the more people you can hit with your Command: Dissonance.

Orianna's passive makes her aa early very potent for trading with the enemy mid laner. This is why you take Greater mark of hybrid penetration because her Clockwork Windup greatly increase chance of good trades early. This is also why you take Command: Protect first so you can shield some of the incoming minion damage when you aa the enemy mid laner. Armor and mr is self explanatory, and ap quints is for the early ap ratio.

You itemize differently if you are vsing an ad mid laner or an ap mid laner. the only real difference is the Tear of the Goddess and the Chalice of Harmony. By the end of the game you would have a Seraph's Embrace if you were vsing an ad mid laner, and a Athene's Unholy Grail if you were vsing an ap mid lane. If by some chance that they have a Vladimir top or an ap jungle or some other ap dealing champion if you build a tear, an Abyssal Mask is probably a better choice than Liandry's Torment.

If you are playing in lane at level 1, you can Command: Protect yourself after you have auto attacked the enemy champion once to proc your Clockwork Windup and deter enemy minion damage. After a few times trading like this, hopefully you would have gained a small advantage
In a teamfight, you need to Command: Protect a tank or an engager like Jarvan IV or Malphite, or Shyvana that can jump into the fray. After your ball deliever has gone to the centre of the enemy team, you can Command: Shockwave, Command: Dissonance, then Command: Attack for maximum damage.
Always remember that her Command: Protect can protect her and her teammates and give the ball holder extra mr/ armor.

Pros
- Command: Protect is a great way to deter some damage early by minions when trading
- If holding the ball after you have skilled Command: Protect, you get extra mr and armor
- all of your skills are aoe, you can always hit more than one target
- Kiting/ peeling is very easy because of the speed boost to allies/ debuff to enemies from Command: Dissonance.
Cons
- If ball is not where it is suppose to be, you can miss your whole combo
- If Command: Shockwave is missed, a lot of your potential threat is gone
- There is no hard cc before level 6
- Ball control can be hard at times

Her Clockwork Windup allows early csing very easy to do. The extra damage from her Clockwork Windupcan allow you to last hit much easier.
Mid game, if you send her ball just behind the last creep in the minion wave using her Command: Attack, you can clear the castor minions with self casting Command: Protect, then using Command: Dissonance to clean up the melee creeps.