Sivir Runes explained
There's one set of runes for Sivir on patch
11.8
that is the clear favorite for LoL players and pros alike. The best Sivir Runes on the position 
Adc are Precision as the primary path and
Sorcery as the secondary path with a pick rate of 49%. Besides runes you should take a look on Sivir Build and if you are interested in pro matches take a look at Sivir Probuilds. If you want to discuss
Sivir then you should visit the champion subreddit.
Primary path on Sivir
Precision improves attack and sustained damage on Sivir troughout the match. Most of high elo players – and our LoL pros in the the major regions – have agreed that
Lethal Tempo is the best keystone rune to run on
Sivir. This keystone rune gives Sivir a great head start in team fights and allows to put out more damage in that time window. This is usually followed up by taking
Presence of Mind,
Legend: Bloodline and
Cut Down.
Presence of Mind helps Sivir with the mana problems by restoring missing mana, if a champion is killed.
Legend: Bloodline gives life steal, which aids in winning damage trades and fights in the later stages of the match. If the enemy team consists of multiple tanks, then the rune
Cut Down is the best choice.
Secondary path on Sivir
When it comes to your secondary path, most
Sivir players prefer to go with
Sorcery.
Sorcery empoweres abilities of Sivir and increases the available champion resources. On the
Sorcery path, the best runes for Sivir are
Nimbus Cloak and
Celerity.
Nimbus Cloak, which grants movement speed upon using a summoner spell, works amazingly well with junglers in particular as they take the shortest cooldown summoner spell,
Celerity boosts all movement speed bonuses to Sivir.