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.
Ok, first steps, try to use the first shoot for the Champion, with the critical chance at 100% is a sure Critical hit and it always a good thing to make them back, you can also combine the critical hit with a rapid Volley.
With the boots you are able to survive and the 3 potions will let you stay enough time to get 1850 of gold for the B.F. Sword, with this Item, you do great damage at early game and if you are careful may be you can kill 1 or 2 champs.
Depending on the champs in opposite team, you can made Berserker's Boot or Boots of Swiftness, Ninja Tabi is also good because of your Evasion runes, that would be a a great Evasion rate.
The other items are Speed Attack, Critical Chance, Life Steal and Damage, these items don't need any explanation.
Regarding your Ult:
With this build you will have almost Ult for every battle, use it to open the fight and stun the enemy so your teammates will have an easy target on them, may be u have ult twice in a single battle.