This is my first build so bare with me.

After playing several games with Caitlyn and trying several builds I found this one to be the most affective going 17/9/9. I not a very consistant player but the speed and crits from this build lets me be more consistant than I normally would be. The other reasons for the speed and crits is her ability powers are not going to net you kills, they are chase powers and farming powers. The only time Ive ever gotten kills from Ace In The Hole is early to mid game where me and my mate couldnt get the kill before he went back to the tower, I locked on and got him.

So please enjoy and leave comments

Headshot (Innate): Every 8 attacks (attacks while in brush count as 2), Caitlyn will fire a headshot, dealing either 150% damage to a champion or 250% damage to a minion

Piltover Peacemaker (Active): Caitlyn revs up her rifle for 1 second to unleash a penetrating shot which deals physical damage to targets in a line, it deals 6% less damage to subsequent targets, down to a minimum of 70%.
Cost: 50 / 60 / 70 / 80 / 90 Mana
Cooldown: 10 / 9 / 8 / 7 / 6 seconds
Physical Damage: 40 / 70 / 100 / 130 / 160 (+1 per Attack Damage)


Yordle Snap Trap (Active): Caitlyn sets up to two traps to reveal sneaky yordles, which trigger on champions. When sprung, the trap immobilizes the champion and deals magic damage over 1.5 seconds. Traps lasts for 4 minutes.
Cost: 60 Mana
Cooldown: 20 / 17 / 14 / 11 / 8 seconds
Magical Damage: 80 / 130 / 180 / 230 / 280 (+0.6 per Ability Power)


90 Caliber Net (Active): Caitlyn fires a heavy net to slow down and deal magic damage to her target. The recoil knocks Caitlyn back.
Cost: 90 Mana
Cooldown: 18 / 16 / 14 / 12 / 10 seconds
Magical Damage: 80 / 130 / 180 / 230 / 280 (+0.8 per Ability Power)


Ace in the Hole (Active): Caitlyn takes time to line up the perfect shot, dealing massive damage to a single target at a huge range. Enemy champions can intercept the bullet for their ally.
Cost: 150 Mana
Cooldown: 90 / 75 / 60 seconds
Physical Damage: 250 / 400 / 550 (+2 per bonus Attack Damage)
Range: 1400 / 1800 / 2200

I'm not sold on these rune set so any suggestion is much apperciated.

Mark of Alacrity to help get the extra speed early game.

I've changed my runes from AD to Crit Chance on the advice of Splinter_Cellz (thx), I like this set up better for the same reason as he suggested

I am considering making all my Quints mana regen as this could free up a summoner spell for me but idk.

I think this is pretty self explanatory as must Caitlyn builds use a similar mastery layout. Basically everything is to help your intial attack dmg, speed, and mana.

Speed and Crit are the rule of thumb here anything that gets you there is the way to go.

Dagger and Health potion are my favorite starters for the attack speed and makes it alot easier for berserker greaves especially if you need to go back for a early return.

After your greaves get Phantom Dancer, these are the beginings of your AS and Crit.

Infinity Edge not only provides the much needed crit chance and crit damage but adds AD to your powers.

After that 2 Black Cleavers for the speed and AD

Those are your core items so what you get for the other 2 slots is up to you.

Dagger: +15% Attack Speed. 420 Gold

Health Potion 35 Restores 200 health over 20 seconds.

Berserker's Greaves: +25% Attack Speed, UNIQUE Passive: Enhanced Movement 2. 920 Gold

Zeal: +20% Attack Speed, +10% Critical Chance, +8% Movement Speed. 1195 Gold

Phantom Dancer: +30% Crit Chance. +55% Attack Speed, +15% Movement Speed. 2895 Gold.

Infinity Edge: +20% Crit Chance. +75 Damage, UNIQUE Passive: Critical hits now deal 250% damage instead of 200%. 4080 Gold.

The Black Cleaver: +55 Damage. +30% Attack Speed. Passive: Physical attacks reduce your target's Armor by 15 for 5 seconds, (maximum 3 stacks). 3065 Gold.

I chose Clarity cause Caitlyn's mana is horrible ( she should be a cooldown champ )
And Exhaust for some added chase down and to help out in team fights but Ignite is also a good choice.

Now that I think about it Ghost could be better than exhaust for the chase.

Pros:
Great range
Great utility

Cons:
Low health
Extremely low mana
and ult for the damage it does takes too long to fire

Take the Q power for its farming capability, its important to constantly farm as if she get behind its much more difficult than other champions.

In this stage, keep behind and use your range to harass your opponent. Its more important to farm than it is to get a kill (your kills will start coming mid game)

In this stage what you want to do is keep farming and push towers by yourself or help others push towers and help gank

Remember to keep farming as you need to money to get your crit to at least 50 (Infinity Edge is your first expensive item)

In this stage stick with the team and stay behind the group, let your range do the talking.
You'll be shooting fast and hard.

Dont forget to set trap and creep in for your slow

Well this is my build, hope you like it. Just remember that the key to get you the speed and crit you need Farming is where its at, I havent seen anyone farm like Caitlyn can