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.
Order of items to buy:
Long Sword and 1 health pot
Sword of Occult
When you start with the long sword and the 2 health pots, it should get you to level 6. You should go back at level 6 unless you got plenty of HP and mana. Anyway, you should be able to buy Sword of Occult by then so I would pick that up. Buy boots the next time you go back because you should be getting kills left and right.
By now you should be doing some good dps, I like to pick up last whisper for the Attack Damage and the attack speed and its nice passive. You will be probably be on a killing spree or even dominating. After you can get alot more gold, You should be picking up the Infinity Edge for some nice damage and your Heartseeker should be hurting alot by now.
You should have alot of dps by now and be getting at least gggggggodlike. As soon as you have enough gold to buy Black Cleaver, you should get it. Then for some lifesteal and AD, I like to get the Bloodthrister and when you get this complete build you will be legendary. You will be unstoppable for sure.