Hello I am Summoner CheesyBoy8. I have played Sivir for a while now perfecting the build and playstyle to share with others.

Flash and barrier are good to take on Sivir, it helps in the early game before your power spike and allows you to take more aggressive trades as you do have some escape. Also barrier synergises well with your E as you get two shields, one giving mana and one giving more resistances.

My ideal build with Sivir is:
Berserker's Greaves
Infinity Edge
Statikk Shivv
Essence Reaver
Rapid Firecannon
Guardian's Agel

Please note that your power spike is after two to three items. The shivv proc will help you clear waves, which is your main purpose.

Max W, then Q, then E. E does allow for more escape yet Q helps with the waveclear which makes Sivir a viable champion.

These runes are about early game survivability and extra late game damage. Fleet Footwork allows you to survive in the early game with the movement speed and overhesl gives you a shield and allows for more healing. You technically have 3 shields to use to your advantage.

Absolute Focus and Gathering storm gives extra AD in the late game.

Sivir can be a scary champion to the enemy team yet Sivir is not a hard carry. If the team is doing well then she offers lots of damage with the right support to protect her. If the team is not doing well it is hard to carry as Sivir to get out of the situation unlike a Kai'sa or Jinx.

Yet waveclear is all Sivir needs. With this skill you can: push waves very easily; siege opponent turrets; siege inhibs and nullify sieges on your own base. Sivir's power spike is after two to three items once she has a crit base of items and she deals a lotta damage. She may be out-damaged late game yet she is still a very formidable opponent.

Is Sivir someone you should learn? Yes absolutely, she is unique and worth learning for the good matchups shown above.