I'm Killleage a diamond EUW player , who loves to play cait:)

Pros

• Huge range(650)--> So you can hit them while they can't hit you ;)
• Escape with her E(Net)
• Q really helpfull for shoving and for poke
• R , nice to finish off an enemy

Cons

• You can E the wrong way
• Not that strong in 1vs1

Marks

9x AD marks are key because you want to be doing the most damage as possible as an AD carry. AD marks will not only let your auto attacks and skills do more damage, but it will also help you last hit easier.

Seals

Armor seals are very core for an AD carry because you will most likely be going against another AD carry and a support. Without armor seals, you're going to be taking a LOT of damage in lane, and thus without these you will never be able to 2v2 against the enemy bottom lane.

Glyphs

MRplvl , because most AP champs do more dmg when higher level (relatively) , so more MR when they hit more.

Quints

I like using 2x Life steal Quints and 1x AD Quint. This is because you still want the lifesteal runes that will help you sustain yourself in lane, while still having a bit more of AD to help you bully your lane harder. If you feel like you just want more scaling into late game, then feel free to take 3x life steal quints, I think this is your own preference.

22/8 dafuq?

Everything you want as a caitlynn you have it , its based on bully them early , if you go for more late game I would suggest going 21/0/9

Why no blade?
Blade is a good item , also on cait , but that is only when facing against HP tanks , like mundo.
Zephyr
Good item especially when they have a lot of CC . Only buy this when you are against a team like : veigar , annie , varus , mao , jarv4 , etc.

Trinity
Only buy it when you know why you are doing it , otherwise just don't do it.
Hurricane
When playing VS bots , you can buy it to push really fast.
Statikk Shiv:
Buy it when your team doesnt have much wave clear.

Flash Barrier
Barrier is just really nice because the shield is just strong.
And you can get a better cleance called QSS
Flash , don't have to explain ?

Flash Ghost
Hmmm , you can try it , I don't like it , I also don't use it on ashe , but it can work for you.

Flash Cleance:
When facing against heavy CC.


Heal: Baiting time I guess

Exhaust:
Possible when your sup goes ignite and you need it VS zed or something idk what.