Hi there, first off id like to thank you for choosing to look at my first guide ever, any constructive criticism would be appreciated, with out further wait ill go more in-depth into my build below enjoy!

P.S in each Chapter ill attempt to explain why/how each build is different (mostly for runes)

The Reason I use these runes are for the following

Move Speed, Attack Speed Rune Build:
Marks of Alacrity x 9 ( + 1.7% Attack Speed) - More Attack Speed for your Passive Skill.

Seals of Resilience x 9 ( + 1.41 Armor) - Being as Squishy as twitch is you'll need all the help you can get.

Glyph of Shielding x 9 ( + 0.15 Magic Resist per level [2.7 at Level 18] ) - Again Twitch is very squishy and is tended to be prime targets if caught in the open of a team fight, so any bit helps.

Quintessence of Swiftness x 3 ( + 1.5% Movement Speed ) - This will help you move across the field abit faster increasing your mobility, allowing you to get behind those champions for a flank, or to chase down those that run away.


Armor Penetration Rune Page Twitch:

Marks of Desolation x 9 ( + 1.66 Armor Penetration ) - Makes you do more damage to those champions that have Armor, and those that dont get hurt that much more.

Seals of Resilience x 9 ( + 1.41 Armor ) - Being as Squishy as twitch is you'll need all the help you can get.

Glyph of Shielding x 9 ( + 0.15 Magic Resist per level [2.7 at Level 18] ) - Again Twitch is very squishy and is tended to be prime targets if caught in the open of a team fight, so any bit helps.

Quintessence of Desolation x 3 ( + 3.33 Armor Penetration ) The same reason as the Mark's

As masteries I go 24/6/0 instead of the traditional 21/9/0 or 21/0/9, the reason behind this is twitch can benefit from nearly everything in the Offense Tree, and as for the defensive tree i go with the armor and magic resist for the same reasons as the runes, to make him that much more sustainable.

my item build works as such in a semi-detailed breakdown

Doran's Blade - 10 Attack Damage, 80 Health, 3% Life Steal; Great beginner item for any AD Champion's.
Boot's of Swiftness - Increases movement speed by 1.
Zeal - 20% Attack Speed, 10% Critical Strike Chance, 8 Movement Speed - Attack Speed is great for twitch because of his passive stacks.
Beserker's Greaves - Increases movement speed by 2, Increases attack Speed by 30%
Infinity Edge - 80 Attack Damage, 25% Crit Chance Unique Passive: Critical Damage now do 250x instead of 200x.
Zeal - 20% Attack Speed, 10% Critical Strike Chance, 8% Movement Speed.
Phantom Dancerx2 - 55% Attack Speed 30% Critical Strike Chance, 15% Movement Speed. - Makes you faster and hit harder as well as hit faster.
The Bloodthirster - 60 Attack Damage 12% Life Steal (Passive: Gain Bonus 1 Attack Damage .2 Life Steal per kill (including Minions) Maxing at 40 Attack Damage and 10% Life Steal, Half the Stacks are lost upon Death) - this item is crucial for survivability as twitch.
The Black Cleaver - 55 Attack Damage 30% Attack Speed. Passive: Your basic attacks reduce your targets armor by 15 for 5 Seconds (Stacking 3 times) - what makes this item amazing for twitch is his ultimate allows for on hit effects which sould allow you to spread the passive to the whole team, if positioned properly.

Skills

Deadly Venom (Passive)
Twitch's basic attacks infect the target with Deadly Venom which deals true damage each seocnd for 6 seconds ( effect stacks up to 6 times). (2.5/5/7.5/10 True-Damage)

Ambush (Q)
After 1.25 Seconds, Twitch becomes Stealthed for 10/20/30/40/50 Seconds, if Twitch attacks a enemy he gains 30/40/50/60/70% Attack speed for up to 10 Seconds, Depending how long he was Stealthed before Attacking.

Debiliating Poison (W)
Slows near by enemy champion move speed by 30%(+6% per stack of deadly venom they have) for 2/2.6/3.2/3.8/4.4 seconds.

Expunge (E)
Deals 30/60/90/120/150 (+100% of Ability Power)(+20/30/40/50/60 per stack of Deadly Venom) magic Damage to each nearby poisoned enemy, Removing the stacks in the process.

Spray and Pray (R)
Twitch gains 15/25/35 Attack Damage and his attacks become long range line missles for 12 Seconds, Dealing 100% Damage and poisoning targets hit, during this duration only 5/6/7 missles can be fired.

Level 1-A: Varies depending on rather your solo lane or bottom; if bottom you go with Debilitating Poison, to help your Lane mate with an early team fight allowing you to focus one target down.

Level 1-B: If in solo lane you will pick "Ambush" for that which the name Describes allowing you to stealth around you lane or others and either pick off a target or, harass your lane, with nearly no restrictions.

Level 2-A: Ambush
Level 2-B: Expunge - The Reason for this is to get that last bit of burst damage required to kill your Challenger.
Level 3-A: Expunge
Level 3-B: Debilitating Poison
Level 4: Ambush
Level 5: Ambush
Level 6: Spray and Pray

Combo should look along these lines when in a Team Fight
Q>R>E>W or Q>W>R>E or Attack>Q>E>R>W

For summoner spells i personally like to use Ghost and ignite, i have never been good with Flash, and ignite ontop of your passive just adds for a nasty amount of true damage being dealt to the enemy.

Thank you for taking the time to read through my guide, i hope it helps you out, and if not still feel free to comment on an mistakes i have made, id like to give a HUGE Shout-out to Boyfriend Rob (KiefCheif)[LoL NA] for staying up with me all night and helping me with the item and ability descriptions. as well as riot for making a fun champion.

Feel free to message me in game, or on the comments i will reply to as much comments as i possibly can when i can.