Pros:

-Great Harasser
-Easy to zone with
-Easy to learn, a bit difficult to master
-Rarely played
-Awesome if you have the Pax Skin (I love it)
-Is a girl. I don't care if you are a guy or a girl, this is awesome.

Cons:

-Frail
-Pushes easily-- great if your support gets wards, bad if not
-See "Counters" section
-After Spell Shield, vulnerable to cc
-Medium range
-Mana hungry until Muramana is built
-Could use a graphics tweak...

Hello~!

My first Sivir game had to be back in around July or August, in an ARAM game. I had no clue what I was doing, and was facing people who had been playing for years. I had a positive KDR. I never played her again, until recently.

As I was looking around, I stumbled upon the PAX Skin. I obtained the code, and ever since I have gotten that skin, I have loved playing her. She is an underused champion that can decimate many ADC+Support compositions, and others as well.

As most players, I relied on Mobafire. I joined late Season 2 to this game, and didn't know enough to make my own build.

But. I'm the type of person who will read 5 guides a day, on champions he doesn't even own. I'm the kind of person who researches different items, and uses a philosophical approach to determine their usefulness. I'm the type of person who puts in a ton of thought to maximize effectiveness.
Come Season 3, all these new changes occurred. It was time for me to take matters into my own hands. I made my own build, and saw my damage routinely double. I played 2 ranked games, and won both-- an even KDR in the first, positive in the next. I should state that ADC is my least (or was) favorite position, and that I have never played ADC in ranked before. Approximately 1250-1350 ELO, but my point still stands.

Please, read on, and I can assure you that you will find what you need in this guide.

As one final statement, I will not be discussing mid lane with Sivir. However, the information in this guide should be able to help you should you find yourself in that position, and although its use would be a rare niche pick, it can be a viable choice.

Over 10,000 Views! Thanks guys!!!

Let's start with Runes, since if you're briefly looking through, you'll probably want to know what I choose, and why.

Reds.

You'll want flat AD. Why? Your Q Boomerang Blade scales off of AD. So do your auto attacks. You are not solely an auto attack champion, nor an AD caster as Sivir. You want to utilize both effectively. Getting flat AD hurts, badly. When I originally started playing with Sivir, I was using my jungle Nocturne runes. These included flat Attack Speed. Bad. Why? They don't scale with her Q. You want AD. Period.

Yellows.

Let's face it. Sivir is squishy. REALLY squishy. Welcome to AD Carries. I find these essential to at least actually survive early game. If you don't get these... You'll drop like a fly. You'll wonder why their AD Carry hurts so much, then suddenly Sona of all Champions kills you. That range...

Blues.

These are what I recommend. In team fights, mages tend to toss around a lot of AoE. This helps against that. Once again, Sivir is really squishy. I do not suggest building survivability on Sivir, but at the same point, you don't want to die in under a second. You need a second to kill someone. ( Blitzcrank: Ha. Ha. Ha.)
If you truly don't like these, there is another option. Greater Glyph of Cooldown Reduction. They cost much, much more (820 a piece, OUCH!), but they give nice CDR. But I take some CDR in my build instead, and would like to survive mages a bit more. Spell Shield doesn't do it all...
You can also go MR/Level, since versus the AD, you're more likely to face AP champs later on in the game, but due to AP junglers like Diana and such, and well, ganks (never know when that Katarina decides she wants to come down and say hello). Also, I just like them :D

Quintessences.
Greater Quintessence of Armor Penetration
I like these. But Glacialwrath! Shouldn't I get Flat AD Quints for more early game damage?! Actually, that is perfectly viable. However, I prefer these A. because I'm cheap and I already had these, but B., the real reason... These scale well into mid/late game. Flat AD is vital for your Marks for early game, no question about it. But these in addition to those give a good, strong early game (not as strong as full AD), while smoothing a transition into mid game. Late game, you're an ADC. You'll wreck period. But yes, if you so wish, flat AD is viable (flat meaning it doesn't scale per level).

Look, I'm a Mobafire guide reader myself. I know this section always hurts to read. So I'll make it easy on you.

I chose the ones that I did for maximum damage output, because I'm an ADC. I have some survivability in my Runes, it ends there. Here, I go for maximum damage, along with a bit of mana regen in the Utility tree.

Feel like something is better? Go for it! But these are what I recommend. "But Glacialwrath, 21 in Offense means I can dive deeper into..." A further Utility tree with Masteries that are less beneficial for killing? Runic Affinity for that Red Buff duration mid-late game, but nothing early? Go ahead if you wish, but I prefer these.

Ah....

See, here's where things get interesting. All of these new glorious items, and the old... I'll go over each in the build, as well as some old ones, and potential.

Yes:

Never start with anything different. Ever. EVER. I used to run Boots, 2 Health Pots, and a Mana Pot. No longer necessary, as Boots are no longer as good of a pick as they used to be, and this will amp up your early game damage. I don't recommend stacking Doran's Blade on Sivir, but I do recommend starting with one. When you sell it later, it only costs you about 300 gold.


Manamune is okay for damage; the increase in mana pool isn't really noticeable until later on. You might actually find it a hindrance early on, compared to other items. But, around the 25 minute mark, give or take a few, you should have a Muramana-- we'll talk more on this later. But, Muramana gives insane damage. Sorry, "tons of damage". That, and once you have a Muramana, mana should never be an issue on top of having great damage. Perfect overall. I consider this an incredibly essential item on Sivir now.


Don't make me explain. Sivir go fast. Sivir attack fast. Sivir do "tons of damage". Dr. Mundo feel pain...
Also, I'd avoid Ionian Boots of Lucidity. "But I can Q more!" Don't get CDR here, get these boots. You -are- more of an AD Carry than an AD Caster (you should still utilize both well), so go Berserker's Greaves. Pray that they smell good after Olaf wore them.


Attack Speed, CDR (more Boomerang Blades), and Tenacity. The Tenacity is really amazing against those high-cc teams, where you wish you had just one more second. But even if they're low CC, I'd still suggest getting this. Because the odds of facing a no-cc (Crowd Control) team is... Not likely.


Originally a first-to-be built item on Sivir. Why not now? A few reasons. One, you want Manamune as soon as possible, to get Muramana as soon as possible. That upgrade takes a bit. Two, I'd say getting Zephyr before this is vital for firing off empowered shots from your Muramana faster, and the Tenacity for teamfights. And, don't skip boots for this. Just don't.


Ah, see, this seems a bit redundant with Siv's ult, yes? No. You can use this while on CD (it happens), or right before. If you need a quick burst, but don't want to ult yet, use this. Or after your ult expired, at the end of a teamfight, to finish up those who may try to escape. A great new item.


Get this earlier if you need the armor pen that badly. Why not Black Cleaver? BC can quickly stack with Sivir's W, Ricochet (it resets the auto attack timer), but it's not as good on AD Carries, and it won't be as good for your Q, Boomerang Blade. Leave Black Cleaver for your solo top or whomever grabs it.


You can certainly use other ones, but I'd go with this. Enchantment: Furor is redundant with your Passive. This helps you with your Passive-- you get extra movement speed chasing someone, and others with you run faster behind you to help. Personal opinion.

Maybe:

A good alternative to BT, if you're facing a bunch of tanky enemies like Darius, Olaf, and Leona (Top, Jungle, and Support respectively). This works like the old Madred's, and has lifesteal along with it. And nice AD. Otherwise, I'd ditch this.

No:

We'll call this combo the "Phantom Edge" combo that was common before. Why? Because "Infinity Dancer" sounds kind of fabulous. And this is a serious guide. So stop that. Stop laughing. ._.
Anyhow, Phantom Edge was common in Season 2. Pretty much all AD Carries used it. It's still perfectly viable, don't get me wrong. However, I prefer Zephyr to Phantom Dancer, as it has CDR and Tenacity over Crit Chance. Those two combined are very nice. However, without PD, you don't have enough Crit for IE. Thus, I dropped that as well, and grabbed Sword of the Divine.


More attack speed than you can ever hope for, that won't proc with Ricochet, that won't work with Boomerang Blade, that... Just meh. This item is okay, but I wouldn't suggest it for Sivir. Still nice though.


Honestly, I think this would work even better than Phantom Dancer now with Infinity Edge. It certainly looks very sexy, and...
Wait, didn't we just talk again and again about Tenacity saving your life long enough to kill someone?
Anyhow, if you really, really don't want Zephyr, I'd actually take this and use Infinity Edge with it over Sword of the Divine. I, however, will keep my CDR and Tenacity. It is an option, but even more risky than I'd ever want to be as an ADC. Which is admittedly pretty risky.

Should almost never be used. I have never used it, and rarely face teams where I should.

I just added it in for those who were asking for other options... This is it. But you need to know when to use it:

When 0 stuns/slows/suppresses/snares/roots/binds/etc exist on the enemy team, then please go with this. The Tenacity on Zephyr will be useless, so I'd consider this more viable, and better for your damage output.

However, it'd be really rare to face a team like this, so don't count on using this build much. You have a higher chance of facing a Viktor, Karma, Heimerdinger, Urgot, and Sejuani on the same team. Almost...

Skills?! I've been wondering why I haven't seen these yet, why so low? Because Mobafire suggested it, and you can look at the skills at the top of the guide. Also, you'll likely quickly re-refer to Items/Masteries/Runes, but not these. So yeah. Deal with it. *Puts Sunglasses on and takes 1 less damage from Leona*


Passive. Basically, this just makes chasing much easier. It also makes Enchantment: Furor kind of useless on you. Never-mind that I actually built that one game. I won. I was ahead. Hush. "But Glacialwrath, I don't like chasing. Mamma Karma (wait, who?) told me that chasing was bad..." So get wards. Or don't be afraid. You're Sivir. You can run out of situations almost as well as Skarner with your ulti. Almost.


Always get it at lv 1, almost always at lv 3, and always max it first. This is... Tons of damage. Yep, I said it again. Anyhow, the damage is reduced, down to a minimum, per... Um... Thing... It hits. So it can be smart sometimes to poke minions and the enemy champion with this while farming if you want to whittle/farm the minions as well as poke, but for more damage in the laning phase, go for a clear shot. Try to hit your enemy on the way forward and back. It should also be noted that this sucks a lot of your mana.
Oh. And please smartcast this. If you don't know how, learn how... It'll make you that much better of a player.


Hey, I spelled it right for once without Google Chrome correcting me! Anyhow, Ricochet is used for last-hitting multiple minions at once, harassing a little bit, and more.
When actually fighting, this resets your auto attack. What does it mean? No Lux, don't answer about the sciency rainbows! Anyhow, what this means is that you can auto-attack, use this right after, and you'll attack faster. Getting out more damage. More damages than a Garen with 6 Doran's Blades. Because you need the damages.


Okay, this takes a lot of practice to get used to. A few tips. Don't blink (seriously, blinking while poking has failed me), and get used to audio cues. This means that listen for the sound of the enemy champion releasing an attack, don't look for the ability flying towards you. Do this, and you should react fast enough to pop this. There are exceptions; if a Teemo rushes towards you, he'll likely Blinding Dart immediately. You can pop this and get free mana. Nunu & Willumps will chuck slush at you slow enough that you can quickly press it.
This gives you good mana regen in lane, and survivability. Both of which you need.
Also good for absorbing:
Caitlyn traps
Karthus ult
Teemo shrooms (guess where they are)
Ashe 's ulti.
Ashe 's Volley.
Most other ADC poke abilities.
Amumu's ulti.
And about a billion other things. This is just utterly amazing. There is one I am afraid though:
Leona. Curse this support. Your Spell Shield will absorb one stun, but not the other. Enjoy...


Guess what Sivir's ulti is? You and your nearby allies become Master Yi for a bit. Yep. Though slows affect you guys still and your allies don't gain AS much of a boost in attack speed.
Do NOT reserve this for teamfights. Use this for Baron, 1v1's, running away, and one of the best uses for it: Taking down turrets. Fast. Really fast. Oh RIOT released Ohmwrecker?! Who cares, you're Sivir!

Overall, R>Q>W>E, with E usually taken at lv 2 for absorption. Your E only reduces in cooldown per level, so it's better to take W for more damage when resetting your auto attacks, and clearing minion waves.

Always have Flash. Always. It lets you get out of really bad situations. Or turret dive, almost get the kill, and die. Either way, grab it. Exhaust> Ignite because it's more reliable, ensures you'll be able to utilize your passive, hinders the enemy in team fights, and more.

Feel free to grab this if your support grabs Exhaust for you.

If you find yourself backdooring a lot; I personally wouldn't take it.

But what about those other Summoner Spells?

Ditch them. Ghost is repetitive with your ulti, Ignite beats out Barrier, Clarity should be taken by your support, unless they have good enough mana restoration ( Soraka, for instance), and... You get the point.

This gets its own section.

In team select, let your support know you'll need a ton of mana regen, and why. Mana Manipulator, Clarity, Soraka becoming a living Mana Potion... All are nice. Communicate that having at least one of these is essential. And that when you get 700g in game, you are recalling.

When you get 700g, you are recalling. Just do it. You need your Tear of the Goddess as soon as possible, to begin charging it. The sooner it's charged (the stacks carry on when upgraded), the sooner you get your Manamune turned into Muramana.

Use your abilities while returning to lane. Constantly poke your enemies. If you won't be using it soon, Spell Shield as much as possible. Use your Boomerang Blade while attacking a turret, even though it won't damage. While running from a bad fight, use Ricochet (you don't actually have to fire it). Spam. Spam. Spam.

If you farm at least decently well on minions, zoned yourself somehow or zoning them, either way, if you spam enough, you should have a Muramana around 25:00. Give or take a few minutes. Consider it like a Rod of Ages, meh at first but once completed, very nice (referring to the Manamune component).

When your Manamune transforms into Muramana, toggle it. Press whatever key it is on your inventory. Make sure to toggle it off when farming minions, but have it ready when you're about to fight.

A final note-- thank you MTaur for pointing this out and reminding me-- if you happen to be laning in a kill lane, after you buy your Tear of the Goddess, buy a Faerie Charm. It doesn't cost much, and you can sell it for almost all that you paid later on. This is by no means as good as a support's replenishment, but it will give you an easier time stacking your Tear than without it. If you don't buy this, you can find yourself wishing you had your Muramana earlier than you will.

To reiterate:

"In team select, let your support know you'll need a ton of mana regen, and why. Mana Manipulator, Clarity, Soraka becoming a living Mana Potion... All are nice. Communicate that having at least one of these is essential. And that when you get 700g in game, you are recalling."

Beyond that, talk to your team. Sivir can backdoor well, and splitpush well.

In a teamfight, just focus the squishiest -available- target. "Why did you focus the tank?" Was the squishy in a place you could safely attack? If so, move and capitalize. But if not, wait for that. You are squishy yourself, but you deal, wait for it, "tons of damage". Also, if you have Exhaust up and ready, use it on whoever looks deadly. Take out whoever is needed, and your job is done. Keep in mind that due to Muramana, your mana will be drained fast in a fight. Good. So will their health.

Here, I will discuss counters, and how to deal with them:

Leona
Okay, this is a tough matchup if she knows what she's doing. She has three stuns, a slow, and her passive makes her ADC deal more damage. You can't Spell Shield all of the stuns. Stay clear of the bushes, stay clear of her, and if need be, you might have to play defensive. Treat her like a good...

Blitzcrank
You are bot lane. You don't like Blitz. He doesn't like you. Stay behind your minions, avoid the brush, get wards. Run side to side. You can Spell Shield his grab but the punishment for missing this is really high.

Tristana
She outranges you. Enough said. If she doesn't abuse it though, she's no worries. If she does, you'll likely be out-harassed.

Ezreal
He's not really a counter per-say, but he is annoying. He can hurt you, you can hurt him. It comes down to how well you avoid his skill shots, and how well he avoids yours. He can avoid yours more easily, but you can still take him down with proper prediction.

Teemo
He is annoying to deal with, and he loves to Blinding Dart you. Abuse the fact that you have longer range, account for the fact that he moves faster (sorry, Move Quicks), and predict his Blinding Dart with a Spell Shield. Use Spell Shield to absorb mushrooms, and gain mana.

Corki
Highly mobile, can easily shatter your Spell Shield since he is a spammer, and an often in-your-face champion. Having a support that can stun is probably your best bet here; establish early dominance.

Twitch
His True Damage DoT (damage over time) from his basic attacks add up, his Expunge really hurts, and he can dodge with invisibility. Predict his Expunge and pop Spell Shield to mitigate most of the damage. He's really squishy, so safely establish dominance, if you can, with your Boomerang Blade.

I'd like to give a picture to my work, and I'll gladly add in others' as well-- send me a screenshot and I'll add it here for ya~!

Also, I would like to thank Mobafire for being awesome, and Jhoi Jhoi for making her fantastic guide on, well, how to make guides.

I hope you all enjoyed the read, and will do well in your future matches. Good luck Summoners!