Caitlyn is probably my favorite character in the game. She is a beast and I absolutely loved playing her from the start. At first i wasn't really sure how to build her but after a little bit of trial and error i came up with this build and i have not had a problem making kids QQ with the exception of a good tank with a thorn mail. But yeah basically i can rape with this build and I'm hoping this build allows you to do the same.

Ghost: Nice to get away when needed. You shouldn't need to use it often since you should be staying behind your team and harassing with your "Q" and passive. I keep it on me any way just in case someone comes from behind as it works well with your 90 cal. net.

Clarity: This is so you can spam without worry. I use so i can harass a great deal early and once the enemy champion/s are at about 1/3 health one more peacemaker and a Headshot and the champion will most likely be dead. Since you may have needed to use your "Q" a decent amount on them you might need the mana to finish the assault. The other reason I keep it on Caistlyn is because I'm often clearing the lane of enemy champions, which means when they come back they have full mana and health while i would have no mana and about half health, or sometimes less. Simply put it allows you to lane for a longer time, which means the possibility of getting more kills.

Piltover Peacemaker

Caitlyn revs up her rifle for 1 second to unleash a penetrating shot which deals physical damage (deals less damage to subsequent targets)

You're "Q" is your bread and butter. If you don't use this skill, you are doing it wrong. If you dont have AT LEAST 75% accuracy with it you are doing it wrong. Now if you really are having problems with it, stay in the bush, but be careful of skill shots into the brush.

Your "Q" is somewhat spam-able so don't be afraid to use it. Since the runes give a decent amount of mana regen, you just have to cool it with the harassing for just a little while and then you can go back to what you want to do. If you decide to use clarity like me you won't need to worry about not having mana to back away from aggressive opponents, just use clarity and then use 90 cal. net to run. Or you could use it, sit and fight, lay a snare under them and back out of their range and hurt them a ton, your choice but the second option is more dangerous.

Now i know what you may be thinking, "3 crit runes wtf is that?" and i understand. I only have those to help my crit chance just a little really early game because if you can land a crit in the early gank on a lane then they'll already have to pot or be dead if it goes really well. As for the rest, Armor Pen is good for dealing extra damage early game as well as helping go through tank's armor late game, and the mana regen help you to somewhat spam your "Q" early game and harass like a boss