During laning phase you aim at perfect minions score, using your Q on enemies preparing to harass you and sometimes to get far standing minions.

You freeze lane at your tower proximity until you get at least 3k net gold. Then you start shoving, squeezing XP out of enemies. As usual, you start to shove before backing. After backing you last hit for some time, then shove.

Huge misplay is using Q on entire wave to try hit some enemies inside it, because your Q do less damage to secondary targets.

Taking Heal as summoner spell proved less effective because your lane has less attacking potential before L6. Exhaust/Cleanse/Ghost are all good and strong spells.

After you get early powerspike of ER + Runaan, you can start win tempo for your team. If your team is good, you use that early tempo for Drakes and Gold lead. If your team is dumb, you start taking over all lanes and jungler camps. Very important to not overextend and never go to sidelanes, because you are not sidelane champion. When laning phase is over, you are playing around your midlane tower spot, rotating over crabs / waves / raptors / red buff.

If your team makes some mistakes, you allowing them to fix those by holding waves and protecting base. When Base Defending, you do not want to leave base, because at that point, if you die, game is over - you are the only wincon for your team, all of your team waveclear lies on your shoulders.

It is standard to have 0-4 deaths per game, if you die more then 4 times, it means you are doing something wrong, or your support has problems.

Try not to cause your support to have any mental health problems, do not type anything ever, do not ping on top of teammates.

Use question marks excessively to show your team that enemies are missing, because sometimes enemies consider roaming when you freeze. Roaming is very bad for such enemies because they omit a lot of XP but for you it is very profitable. Do not follow missing enemies, continue freezing and farming until you obtain items to shove. Never shove early.

About itemization, it is your priority to reach ER+Runaan early because of both raw stats these items provide and because of mana regen/CDR requirements.

You cannot get any real source of CDR other then ER, so I go for Transcendence to get extra 10 for total of 30 CDR. This amount of CDR is a great powerspike at midgame exactly when you already have items. Gathering storm helps with extending this midgame spike into late game.

Presence of Mind || Overheal?? I tried them both and none proved good enough in all situations. But the Presence of Mind is making you able to extra shove the lane after successful ganks, giving you extra tempo advantage, so I prefer it more.

Cut down || Coup?? Coup is making more worth early, so I like it less then Cut Down. Cut Down is stronger when you will carry later, so I chose it.

Late game is when you buy Botrk+PD+BT for damaging HP heavy enemies. Critical chance is only good early, later you need %HP damage. This is major weakness of Sivir building path, which is bottlenecking her from having perfect game and having OP game stance. If you learn how to play around it, you mastered this champion. PD is providing late game kiting for beating enemies. BT is providing Final Fight Capabilities to close out games.

Sadly it is not possible to recommend going Full Crit in this meta, because Crit builds are very weak against Super Tanks, which have invaded all games. Every time you are losing you will find you have Super Tanks in opposing team: Poppy, Ornn, Volibear, Mordekaiser, Mundo. You have to build percent HP and armor shred. When you have enemies without health recuperation, you can even go Dominik to get extra more armor shred. Mortal+Botrk is mandatory combination nowadays if you plan on doing some damage. When you have 0 tanks on enemy team, you can go Infinity Edge for extra 10% plain damage.

Also do not forget about defending. Against heavy mage comps get Wit's End. Against heavy AD rush PD and Executioner. Executioner is very effective on you because you can spread it like decease in every teamfight.