Not Updated For Current Season
The focal point of this build is not only to propose a suggested item purchase order, but to introduce a custom play style. A detailed description will be provided in the following chapters. Enjoy!
As we all know, Sivir is a per-hit character and, therefore, Attack Speed is vital. A 22-25% bonus is great, and should be implemented by all Sivir users. However, the rest is up to the player, as the runebook as well as the masteries skill tree should fit how you play, and what you are good at.
That being said, apart from the AS bonus I opt for armor and magic resist, as Sivir tends to be squishy. This provides a bit more survivability early on. However, CD reduction, crit strike, and mana regen are all viable and should be chosen by YOU.:)
It is important to remember that masteries should complement the character. Again, it is up to you, but I use a hybrid 9/0/21. Focus on movement speed, mana regen, attack speed and CD reduction.
If you have a strong mana regen runebook, then by all means go for a more aggresive 21/0/9 build. However, keep in mind that Sivir is somewhat mana hungry, early and mid-game. Don't focus only on physical attributes such as AS and Crit in both your runebook and masteries tree.
The item description is beneath, intertwined with the stages of the game. However, I will say that I believe in a balanced game. I prefer a zig-zag of defensive and offensive items to be able to survive and dominate throughout the game.
Make sure you are soloing mid. First, get a Sapphire Chrystal and a health pot. Always select you W skill first. This is particularly important for Sivir. I'm going to be a bit up in some people's faces and say that it is irrelevant who you are lane-ing against. If your opponent is a strong harasser, exchanging blows with him/her is unwise. Sivir is squishy early, and an exhaust + ignite and a little bit of CC will render her easy prey. If your opponent is not good, then you will be able to push him to the tower and eventually destroy it.
The extra mana you get from the SC will enable you to virtually keep your W skill on forever. Put every available point into your W skill (when you can). When it gets to LVL 3 you will be able to harass from afar. Focus on the minions close (but don't get too close) to your enemy. When your attacks bounce off 3-4 times, you will be hitting your opponent constantly, provided you target minions near him/her.
However, champions like Fiddlesticks will just be better than you early on. Put one point into Mana Shield (E) and try to time his harass. Keep your distance and try to proxy-attack your enemy. NEVER go into direct confrontation with the opponent unless they make a mistake, or are being overly confident.
Also, a good tip will be not to use Boomerang Blade (Q). Level it, but don't use it to harass or farm. It's mana heavy. If you restrain yourself from using it, you will alter your opponent's timing, and, when you DO use it, it will probably hit them.
Your purpose is not to gank (but do so if you can) early on, but to out-farm them two-to-one.
By adopting the conservative play style described above, and by focusing on farming, by the time you hit level 6 you will be able to afford a BF sword and a pair of boots of speed. This is where the fun begins. Go back to your lane and keep pushing. By pairing up the BF sword with your leveled W skill, you will be able to clear a wave of minions in a matter of seconds. In fact, if you have Clarity you might opt to throw a few boomerang blades which will pretty much let you get every single minion kill. The BF sword also makes your Boomerang Blade even deadlier.
Keep farming mid until you destroy the tower. Those who believe that Mid should eventually switch lanes and try to gank will be disappointed. Sivir has no stun, snare or any other CC ability. Her ult is made for pushing and 5v5 team fights. On the other hand, staying in the lane will produce gold equivalent of that acquired by killing champions.
Now, by the time you have destroyed the turret, you should be able to turn your boots into Ninja Tabi and a Catalyst. The boots are pretty self explanatory - they stack with her passive. However, if your team is rocking the house, go ahead and pick up Berserker Greaves.
The Catalyst, on the other hand, should always be turned into a Banshee's Veil. This is crucial. It is important for Sivir to keep up her auto-attack in team fights. A Veil in tandem with her Mana Shield will allow her to absorb 2 CC abilities in a team fight. Hence, in order for the enemy team to stop you, they would need to use up almost all of their CC (provided that not every single enemy champion has a stun - but it is possible).
Even if you die your team will clean up.
From this point on, there are different possibilities. However, I usually turn my BF sword into a Blood Thirster. Afterwards get a Starks Fervor, and a Black Cleaver. Keep farming, getting your jungle buffs and support your team.
If the enemy has a fed up tank like Mundo or Malphite, make sure to forgo the Cleaver and rush a Madred's Bloodrazor. However, this should be recognized early and you should already have a Mardred's Razors.
Some people like to stack blood thirsters. I find this to be quite counter-productive. In a competitive game you might always get killed. Losing 120 damage and a ton of lifesteal(3 BTs) every time you get killed renders you trying to farm up your items when your team needs you.
I prefer a more reliable item build.
If you are having problems with CC or people focusing you opt for a Frozen Mallet. It's always a great item on her for survivability as well as chasing them down.
Also, in the VERY late game, if you find yourself having excess cash, sell your boots and get a Phantom Dancer.
I apologize for the long description.
To sum up, focus on farming early on. Get your BF sword as soon as possible and push their towers. Get a Banshee's Veil every time and you will be unstoppable!