I picked up Sivir on saturday and this is what I run:
Meki with 2 pots
Teleport back to get Chalice & boots (normally beserkers, but depends)
Last Whisper (armor pen works on towers apparently)
Runes I use attack speed marks, dodge seals, mana regen / lvl glyphs, Flat HP quints
Masteries I use 8-22-0 build. Offencive I get crit and Attack speed. Defencive I get armor & MR, dodge, nimble, hard skin, Veterans, Ardor and Tenacity.
I feel I do really well with this build, I hope this helps! Also pick up golem buff around level 7. Good luck