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.
I do a 21/9/0 , getting all the essentials in offense but skipping crit and crit dmg and ignite. In defense i get 1 point in armor and 3 in magic resist, after that i get 4 in dodge and 1 in dodge/movement.
I start out with Mark and get Crescent Slash at 2, at 3 I get another Mark and after that I finnally get shroud. Ult at 6, and then i alternate between Mark and Slash, getting mark first, ult whenever possilbe.
Glyphs: Flat AP
Quints: Flat AP
I get flat AP so at start i will have both passives with longsword. Dodge in my opinion is good for any melee ranged characters, you can also get hp/lvl if dodge is too expensive.
Start with a Longsword and 1 potions and head to a side lane. the next time you blue pill you should at least have enough for Wand and boots, if not then get boots. Get guinso when you have enough and start on Rylais with wand first, then giants belt, followed by the tome. When getting lichbane, get sheen first then wand, and start one hextech if the game continues(I've only made it to Black Cleaver twice) and Cleaver after.
Go to side lane and try to lane with a tanky partner, they do not necessarily have to be a tank(Taric is my personal favorite, garen etc...) Do no be too aggressive and get whenever you see a minion with below 60%, mark and hit it for the kill. Always try to last hits because you are a little item dependent. When you hit six, you can start harassing. Put smoke where your oponent is farming and get in it, most people usually (idk why) stop farming and walk in circles in the smoke. Mark and hit once, then go invis again, then Slash. Most of the times they will now walk back, if they are squishy then they are less than half alrdy, pop your combo (Mark-Dance-hit-Slash-Dance-Repeat) if you think you can get the kill, dont turret dive. Go back and get ur guinso and boots head to mid game :D
With Guinso and maybe a 2nd Wand, you are now incredibly dangerous to squishies(ashe, twitch, veigar etc....) continue pushing with your team mates and try not to get caught alone. When in team fights, never initiate. Wait until the madness starts then jump to the squishiest or the easiest, fastest kill. Dance-Shroud-Mark-hit-Slash-Repeat. If you see your hp drop drastically then stop attacking and go back to stealth. Do not try to get into 3 or 2v1's because you are a assassin with huge single target dmg, but rather squishy.
At this point if you were doing good mid and early, you should be death with boobies. With Lichbane, your Mark-hit combo now knocks off insane amount of hp. You also push towers rather well because of your passive, so use it. If you played your game right, everyone will run when they see you, and if caught in team fights, they will focus you. play cautiously and rip squishies appart whenever you see a clear shot.
This is my 2nd ever guide, please comment, rate, and tell me what i can do to improve.