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.
You will want to focus on a possible gank before the minions spawn so you can immediately buy the first avarice blade. If you are unable to get the gank wait until you are level 6 to try for a kill. Let the other team push you to your turret use your ultra on them and go for the kill. Do this whenever you have your ultra.
If there is a tank on your side you will want to skip buying the phantom dancer and buy the ghost blade first. After you run out of space to buy items sell avarice blade and ninja tabi. Also if the other teams tank is a problem you may want to buy another ghost blade instead of that last phantom dancer. Also if you are getting enough kills early you can buy a gunblade instead of the bloodthirster.