Caitlyn hails from the technologically advanced city of Piltover and this is easily reflected in her skillset.
Outfitted with some unique trinkets, Caitlyn gets two utility spells, a long-range damage dealing spell and a very powerful (if rather clumsy) ultimate. Caitlyn's first utility spell, Yordle Snap Trap, allows her to place up to two traps on the ground, and any enemy champion who walks over the trap takes a small amount of damage while being snared for 1.5 seconds.
Her second utility spell, 90 Caliber Net, blows Caitlyn backwards while also firing a projectile forward that deals damage to, and slows, the first enemy it hits. Caitlyn can use 90 Caliber Net to push herself out of harm's way, or to hop up ridges.

On the damage-dealing end of the spectrum, Caitlyn's passive, Headshot, allows her to deal 150% damage (250% on a minion) on her 8th attack. Shooting from the brush allows her to build Headshot twice as fast. Caitlyn's main 'attack' ability, Piltover Peacemaker, is a 'straight shot' spell that, after a brief charge-up time, fires forward in a straight line, dealing damage to all targets in the way. Piltover Peacemaker can damage multiple targets but, much like Sivir's Boomerang Blade, the damage is reduced by 6% per target hit after the first (to a minimum of 70%). Caitlyn's ultimate ability, Ace in the Hole, allows her to pick a target at long range, where she will then charge up to fire a slow moving bullet towards that target. Her ultimate deals a ton of damage at any stage in the game (it scales at +2.0 per bonus attack), but enemy champions can intercept the bullet (and take the damage) by walking in front of their teammate before the bullet hits.

If you think you haven't enough Armor or Magic resist, you can replace your " Black Cleaver " by " Guardian Angel ".

--> Guardian Angel is more usefull in Teamfight, because you have more resistance and if you die, you revive again later.

You can replace all the items execpt the two Bloodthirster and the, Sword of the Divine.
These items are three main items of this build.

With Caitlyn it's easy. When you are between the level 1 at 9 : You are cheated !
-> You can kill any character.

The difficulty is to keep this power during all the match. For this you need to be feed for buy all your items.

To keep this power is more easy if you are at the middle or on a lane WITH a Tank.

I chose to privilege Piltover Peacemaker and Yordle Snap Trap because 90 Caliber Net is only use to slow down the enemys, enter or go out of a fight and to hop up ridges.

1 VS 1 : When my pasive is ready, I use 90 Caliber Net to enter in the fight. I hit the enemy and put immediatly a Yordle Snap Trap (where he go) and use Piltover Peacemaker if he run away.

5 VS 5 : I select a enemy, hit her with my range attack, when Piltover Peacemaker is ready, I use it. To use 90 Caliber Net to slow down a enemy.
I Put Yordle Snap Trap one can everywhere in the melee.
If the enemys are low life, I use Ace in the Hole to finish them.