Welcome to this build for Miss Fortune. If you are having trouble using Miss Fortune, this is the perfect build for you! :)

Pros:
-Alot of Damage
-Has abilities that improve your chances of killing someone, not useless junk
-Just, plain good and sexy
- Noob Stomper

CONS:
-Squishy as a squeaky ball
-no escape methods
-usually focused hard

Some people will ask me in game
WHY DO YOU PICK IMPURE SHOTS FIRST AND NOT MAKE IT RAIN OR DOUBLE UP??
This is the reason
-Make it Rain: Mana Hungry like a Snorlax
-Double Up: Doesn't do as much damage, as i will explain later.

Level Sequencing
take impure shots first. Trust me. that extra Magic Damage you get from those will rape health when they find you in early brush invades. The more basic attacks you get on them, the more magic damage you deal.

SO MAX THAT OUT FIRST. I WILL EXPLAIN WHY

After maxing impure shots, I recommend maxing out double up as quickly as possible.
If you cannot catch up to finish them off, or want to poke some enemies, use this as your poke. It travels through two opponents, so that should annoy them a bit.

MAX OUT MAKE IT RAIN LAST
WHY? I hear you say, WHY?
I'LL TELL YOU WHY.
This ability is almost useless. As mana hungry as it seems, it does pitiful damage to others and slows them down. The slow may be good sometimes, but most of the time, you will find yourself depleting your mana due to this ability. ONLY USE IT WHEN YOU NEED TO.

Take your ulti whenever you can.
dealing 65(+_) per shot and slows, this ability is great for finishing off people. It is an AoE ulti and is a channel ulti, so be careful when playing agasinst annoying douchebaggers like Blitzcrank or Voli.

and Finally, her passive. Mf's Passive, strut gives her extra movement speed when out of combat. when hit, her passive becomes cooldown. Annoying? Sometimes. If anyone, EVEN MINIONS, get a good poke on you, your passive is down. It doesn't matter what touches them, even a stubbed toe would stop her passive. Stupid.

Miss Fortune is based off Attack damage ALOT. basically, you want your basic attack to finish the job, not your spells. This is when impure shots and the two phantom dancers (which some will call me insane) comes in. Pop your impure shots everytime you go into a fight with another champ. just remember, you are really squishy. refrain from playing too aggressive. If you are halfway through this build following everything I've given you, you should have 5+ kills.

Miss Fortune is easy to play. Just let basic attack do all the work. Can't reach them? maybe your make it rain can. Pop it down, slow them and finish them off with your basic attack. ONLY when they are about 400 health or below should you use your ulti. ONLY use your ulti if your ulti can hit them x amount of times enough to kill them, or else you have wasted her ulti. 115 second grueling cooldown awaits you.

I will keep this simple.

2 PHAMTOM DANCERS
As I said, insane basic damage output plus impure shots PAIRED UP with insane DPS is anyone's nightmare on the other team. with the full build, you can do about 600-700 damage to them EVERY SECOND. these killers also give you extra movement speed,so when your strut is off, you can consolidate with even more movement from these phantom dancers.

IE
Typical for any ADC

BLOODTHIRSTER
Life steal and attack damage. Enough said.

LAST WHISPER
Tank Shredder and a *just to make sure i can go through any armour* weapon. Enough said.

Berzearker's greaves
Enough Said.

OTHER ITEMS
These you can consider:
MAW OF MALT: Get dat extra magic shield if against hard APCs or annoying ones
Black Cleaver: to get through dat armour
Guardian Angel: ONLY pick this up if you're dying alot. Helps you take less damage.

I picked 21:9:0

All AD masteries and a tad bit of defence to keep you protected in early game-mid game. A life saver.
and again, Enough said about the masteries.
for Defensive masteries, fiddle around it to see which ones fit you the best. These masteries I have on the build fits me.

again, I hear you shouting into the computer
ARMOUR AND MAGIC RESIST RUNES
WHAT IS THIS TREACHERY
*alt+f4

HEAR ME OUT
mf is so squishy you will die from alot of cc, since squishines plus no escape method is a death sentence. Even Caitlyn has something you can call escape method. Mf? NO. Nothing. The Slow doesn't count.

The armour will save you. Trust me. the magic resist? Same thing.
Enough Said.

RECOMMENDED
-Flash: any level 12+ would take this for adc. a way to get close and get a kill or to escape.
-Ignite: Kill securing when you cannot finish it off by yourself. All adc takes this after lv 7
Ghost: if you're not level 12 yet use this to escape.

THE OK MASTERIES
Heal: new to mf? scared of dying? use heal, it's ok.
Exhaust: pop this on any enemy low on health or trying to run and destroy them with your basic attack combo I have taught you.
Cleanse: WHAT? CLEANSE??? yet again, let me explain. MF has no escape. if you are caught in cc, dead. cleanse followed up by flash can help you. Think of it this way as well. You got snared by someone you're chasing. Pop cleanse, continue the chase, he or she dead. Made my point? Good.
teleport: to get to sticky situations your team is in to get a penta. A way to travel around the map quickly. Works on Mf.

NO JUST NO
clarity: YOU ARE BASED OF BASIC ATTACK. Enough Said
Promote: Are you support? No. Even supports don't take this one. Enough said
Clairvoyance: OK OK, WAIT. NIDALEE CLAIRVOYANCE WORKS THOUGH, AND SHE CAN BE AN APC. Not on Mf. She doesnt have any skill shots whatsoever. your vision is what you get in front of you or where your other friend in bot lane is. Enough said.
Revive: Enough Said.

This build will ensure you 5+ kills. You will get better if not. Trust me. The way of the Basic Attack is strong in this one.
Take Sarah Fortune into the fields of Justice, and give them the liberty to die under basic attacks.
Good Luck Summoners.