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.
The build I have been going with has changed slightly due to ranked games being more demanding. So far I am still going with speed runes for the early game. As for the item purchases - I start off with the vampiric scepter, save up enough money for berserker's greaves and then finish off my first bloodthirster. I then work on the phantom dancer ... usually get zeal first then finish of dancer when I have the money. Most ranked games I have been in allow me enough time to get a 2nd bloodthirster and finish, however if the match is still going on I'll work on the 3rd bloodthirster and finish up with an Infinity Edge.