Not Updated For Current Season
I follow a pretty standard 21/9/0 for this build; I've considered a 21/0/9 for better teleport and faster leveling, but twitch is so frail that a little dodge can save your life.
I get Ambush first always because you can check bushes to avoid walking into a trap for first blood. after that I try to max out Expunge as soon as possible, and Debilitating poison at lvl 4 when you cant get expunge. Grab Spray and Pray at lvl 6 and go on a sequence of maxing out Expunge, then grabing Ambush-Debilitating poison one after another, grabbing ult whenever possible.
I grab ArmorPen, CritDmg, and Crit% for my runes.
Start with a Vamp Scepter and head down to lane. If you are mid then stand behind your turret and when first wave of minions walk pass you stealth, and walk out to lane, maybe lane some hits on you opponent or start farming. If you are at side lane, check the bushes for enemies before you partner go in, and attack them if they are easy prey (most of the times i don't becoz you need to farm and cant risk dying)
go back to spawn when you gathered enough money for Malady and then you have 2 options. You can either teleport to lane and continue farming or you can gank a low hp champ of another lane. use your teleport and teleport to a minion that your oponents can not yet see(Fog of War) if you want to gank. Pop ambush and inform you team about the gank. attack and you will most likely succeed with a kill or assist. Look on your map again for any potential ganks, if not continue farming, grabbing lizard if you have time.
Your items should look like this: Malady-boots-Bf Sword. Maybe even a Pickaxe if you did well ganking. At this point you should be picking off unsuspecting players that are laning alone, you should have no problem against a squishy champion. (ashe-yi ect...)In team fights, you want to be the last to start attacking, that means when everyone is spamming their abilties and busy, pop Spray and Pray and aim for the squishiest targets, you should be able to rip them and whoever is in you line of fire apart.
By now you should have a Phantom Dancer if the other team hasn't surrendered yet. This is when ganking is no longer something you can do often since people usually stay in groups. Depending how fed you are, you should be able to get a couple of multi kills in team fights.
The order I usually go with is
If the enemy team has many strong tanks viable options are:
1.Before you get Infinity, get a Madreds Bloodrazor and skip first phantom dancer
2.Replace Infinity with a black cleaver
3.Replace Phantom Dancer with Last Whisper
If you are getting focused a lot in team fights and cant last more than 4 seconds:
1.Replace Bloodthirster with Frozen Malet, it helps you catch people and give very good survivability.
For max dmg for games that last 60+ minutes, you can sell boots and get a black cleaver
This is my first build, tell me what you think and what i could change/improve. I apologize for the lack of images and maybe bad layout.