Well, here is my first guide for Caitlyn.
I am at present Silver III in position of adc or apc.
I like this position because she allows to be gourmant on the farming and on the kills without being has shelters of any rests.

Pros

+ Great early game with her range of 650.
+ Lane control with Yordle Snap Trap.
+ Able to escape with 90 Caliber Net.
+ Able to pick off opponents with Ace in the Hole.
Caitlyn is a strong champion early game, and as previously mentioned, a lane bully. Her starting range of 650 is the main reason why. With that range, her passive, Headshot, and Piltover Peacemaker your enemies will have to watch out for their positioning. You already have a lot of power, so why not have some more? Yordle Snap Traps will allow you to zone your enemies with smart trap placement. If they step on a Yordle Snap Trap, you can wail away at them. Because of Piltover Peacemaker, you may find yourself pushing the enemy pretty hard. This will leave you vulnerable to ganks, so 90 Caliber Net can help you escape. Lastly, your ultimate, Ace in the Hole is great for picking off any fleeing, low-health enemies! It can also be used as a poke once you get back to lane or before you leave lane.


Cons

- Weak to all-in/close range fights.
- Piltover Peacemaker damage is reduced through each enemy hit.
- 90 Caliber Net is easy to interrupt.
- Ace in the Hole is easily blocked.

While Caitlyn might excel at being a lane bully, she does poorly in any straight up 1v1 duels, or close range fights during lane. Her main harassing ability besides her autoattacks, Piltover Peacemaker, is reduced in damage for every enemy it hits. If you hit your enemy through a huge wave of minions, they won't take an incredible amount of damage from Piltover Peacemaker. Caitlyn's escape, 90 Caliber Net, is easily interruptable by things like Thresh's Flay and Janna's Howling Gale. It's a less than optimal escape tool. Lastly, her ultimate, Ace in the Hole, can be blocked by anyone on the enemy team. It's not an incredibly reliable ultimate, but it'll do the trick most of the time.

// Fury increases your attack speed by just a bit, while Butcher helps you last hit minions, which is useful early on.
>> Deadliness gives you a little AD.
// Havoc and Weapon Expertise both increase your damage, which is most noticed early on. The armor penetration from Weapon Expertise is most handy though.
>> Lethality gives you some increased critical hit damage. Brute Force is more of a point filler.
// Frenzy goes well with Lethality because of the extra attack speed after you get a critical hit. Sunder gives you armor penetration.
>> Executioner helps you deal more damage to low-health opponents.

// Summoner's Resolve benefits your defensive summoner spell. It could be Barrier or Cleanse. You can never know if that extra tiny bit of cooldown reduction will save your life or not.


>> Summoner's Insight reduces the cooldown on your Flash, which is vitally important. Meditation helps your mana regeneration, mostly in lane. Caitlyn's spells can be overspammed.
// Mastermind is another helpful mastery to have your summoner spells on the lowest cooldown possible.

Zephyr is a legendary item in League of Legends.
25 attack damage = 900g
50% attack speed = 1500g
10% movement speed = 595g
10% cooldown reduction = 317g
Total Gold Value = 3312g
Zephyr is 116.2% gold efficient without the passive.
The lowest base movement speed in the game is 325. At this speed, Zephyr grants 32.5 movement speed.
The movement speed stat only increases flat movement speed, and will not interact with other percentage increases.
Zephyr is an excellent choice for many bruisers and fighters, granting them the movement speed and Tenacity to stick to key enemy targets while supplementing their DPS.
Champions with powerful on-hit effects can use Zephyr's attack speed boost to its fullest, such as Irelia's Hiten Style or Jax's Grandmaster's Might.
Zephyr is useful for builds that rely less on critical strike chance, and combines well with the Blade of the Ruined King passive. And benefits AD scaling abilities better than Phantom Dancer.
Zephyr is one of the new Tenacity items added in the Pre-Season 3 Patch. It provides players more freedom in their choice of boots, specifically those who want Tenacity but do not want to commit to Mercury's Treads for it.
Zephyr is an excellent choice for AD carries who have a fully stacked inventory and want to sell Berserker's Greaves or Mercury's Treads for a more expensive alternative.