Lane safety for late game scaling.
Creative tools and rule bending
Get Summoner Shards and exchange them at the shop to change your Summoner Spells during game.
You get free boots at 10 min. but you cannot buy boots before then. These boots give additional MS. For each takedown you acquire the boots 30s sooner.
Get a free biscuit every 3 minutes, until 12 minutes. Biscuits heal and permanently increase your max mana.
+5% Max CDR
+5% Summoner Spell CDR
+5% Item CDR
+20% Potion and Elixir Duration
+20% Attack Speed
Excess healing on you becomes a shield.
Takedowns on enemies grant permanent Attack Speed.
Unsealed Spellbook on Sivir allows you to have your Heal and Flash up constantly making it incredibly difficult for the enemy team to gank and kill you successfully.
Magical Footwear is an all-around great rune as it's basically a free kill's worth of gold at 10mins.
Biscuit Delivery allows you to trade and poke consistently in lane and sustain off any of the incoming damage.
Cosmic Insight is another all-around great rune choice and the extra bit of Summoner CDR makes it even harder to kill you.
Overheal pairs nicely with Targon's for lane sustain and absorbing damage/poke in short trades.
Sivir is highly dependent on getting in as many Auto Attacks as she can to deal damage, especially in the late game where [W] can take over a teamfight.