So as many of you might know Sivir was int season 5 a must play champion in competetive league of legends. Eventhough she got nerfed quite decently she is still my favourite adc. She is very strong in team fights because of her ultimate and also with her spellshield and passive + Ultimate she has got a decent amount of self peel which might be very good, esspecially in lower elos. Her worst part is her low auto attack range and if you cant block abilities and esspeacially in the early game you will have many mana problems which will get solved by buying essence reaver and the fact that you will block more spells in the mid/late game. Very important to mention is her hilarious good wave clear. In the mid game you will be able to kill all 6 minions of a wave with a q and the 3 autos of the w. In the late game a rotation of 3 w will kill an entire wave. Coming the her powerspikes she has defintely not quite the best late game because of her low range and her affinaty towards assasins, well she can kill them but if they are fed and not rely on 1 ability they will most likely pop her instantly because of no escape tool, but however with her auto-attack reset and some huge outplay potential with her e and supporting abilities with her ult she is a late game carry but not damage wise but team wise. So if you have a fed tank he can just run into their adcs face while sivir blocks the most important damage spell of the enemies caster and the teamfight is probably won.

Sivir has of course unique skills but the are not many things to consider the mechanicly master sivir.
W is a auto attack reset
You always want to hit your Q that it hits your enemy twice
You have to time your spell shield very good --> Many people will try to bait your spell shield
or will fire out an unimportant skill before hitting the important skill --> you have to react to that very well.
About sivirs ultimate i only can say: just activate it when you want to engage/disengage/catch up.

For the skill sequence you want to engage with your ultimate to get the movementspeed then auto -mid animation w auto q meanwhile block potential important skills of your enemy and then kite/chase with the help of your passive

Pros:
Very good against champs that rely heavly on 1 skill
Very good wave clear
Very good engage tool
Always a save lane / deny almost every support

Cons:
-Low auto-attack range
- If caught you are most likely to lose

As i already mentioned in the introduciton, farming with sivir is quite easy.
In the early game her farming potential is like with every other adc but in the mid to late game she can clear waves in 2 seconds. This insane clear speed will help you to team up with your mate and force a fight while their adc is still wave clearing or you can potenically even farm the jungle to get even more of and cs lead.
To come back to the early game:
Her q does literaly 0 damage in the early levels and without any bonus ad so i highly recommend not trying to last hit with q at lvl 1 or lvl 2 in q later it becomes a huge damgage spike.
Also as i already mentioned her w is an auto-attack reset so if you are about to miss a creep you can w to get it. That really can save up to 10 minoions in a normal laning phase which are 200 gold.

For runes i take ad reds armor yellows half atkspeed half scaling mr blues and ad quints

you can defenetly change your runes according to your play stlye you can go full mr blues,
half scaling and half flat mr blues, health yellows or even get some cdr or mana in the blues but i prefer it that way

The items are a very crucial part of this guide. I don´t think i play Sivir diffrent to other Sivir players.
When im first backing I would try to get my Bf sword (1300) + 1/2 pots and a pink ward this will potentially happen around level 5 if im not wrong around the 6/7 minute mark.
So your first back should be at around ~1400 gold.
After that you want to get Stattiks stich/rapid firecannon.
About the time you complete Stattiks/rapid firecannon you should already have the tier 1 boots (300 gold)
The next back you should aim to get some life steal (900 gold) + upgrading your boots to tier 2 (800 gold).
Then you want to complete your BF into an Essence Reaver.
After that you probably want to get some more lifesteal by either upgrading it into and bloodthirster or into an mercuray scimitar. I mostly prefer the scimitar but it also depends on the enemies team comp. You can also go for the more damaging option in the infinity edge
Now that you have your stattiks your boots your essence reaver and your bloodthirster/scimitar/inf edge you can go for the new last whisper if the enemy team is very tanky or you go for the other one of bloodthirster /scimitar /inf edge. I cant really guide you on that point since this is very optional and depents on your and your enemies team comp.
But a full build should look like the following :
Bloodthirster/stattiks/scimitar/inf edge/essence reaveer/boots/blue trinket
With this build you have 30%lifesteal a qss, 30%cdr and 70%crit chance.