Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
At first mana will be a problem so work towards getting some mana regen and hopefully manamune will aid in dmg and mana regen. I prefer ninja tabi boots for the doge, but you can judge what type of boots you will need in a particular game. the early lifesteal with the item choice of increased attack speed will become more powerful as you go by. Your choice of preference in whether to use The Black Cleaver or Bloodthirster but usually you wanna have someone at your side at this stage of the mid to late game. Just act defensively and keep your distance.
Hope it helps some or give grounds for experimentation with Sivir, Good luck to all!!!!
(this is my first build, so please be gentle with the comments i would like to improve the way builds are made in this site)