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.
Start by getting you shadow walk to scout ahead to see who will lane against you. Lane with someone who can solo later because you'll be out ganking.
So start by farming creeps, you REALLY need to farm. Last hit minions to get the gold till you reach level 6. By then you'll probably be working on your mobility boots or your lich bane if you're ahead.
Start by checking you map and see which lane has more trouble, and go there but stealth before you reach them so they don't know you're there and start with ravage, keep auto attacking and spamming, and if your ult was available, turn it on before you ravage. Keep doing that in every lane don't just stick to one. If they start attacking you while they're stealthed have your team-mates check out who has oracles elixir, and if no one has it get oracles elixir and look for their vision wards and kill them. Now you're free to roam again =).
Keep doing that and you'll be pretty fed, but the last point of advice is never attack a tank, you'll just waste your abilities and he will most propably kill you then. In team fights try to take out their weakest link, they're carry or their support, like Ashe or Soraka.