this build may look strange for an ad ranged, but with the warmog combined with atma u get 60 damage and critical + high health and 48 armor , this combination makes mf sirvives double than normal builds, and you can survive most of the fights and the ult in the best place , you can use flash to run away OR to flash to the best place for ult, one good aim and u win the fight.
this build has lower attack speed than other builds and thats why i upgrade the (W) skill first.
i tried this build and found it gives enough damage and u never be scared from being killed in 2 sec by master yi or tryndamere or annie.
if the enemy has more ap users , u can change the madred to banshee.
this is my first build , i hope u like it :)

since mf is an ad ranged , the its obvious that she needs offence masteris,the magic penetration is to inhance her ult, 1 utility to enhance flash.

mark and quentessence: use armor penetration
seal : use armor to increase survivability in lane
glyph: use magic resistance at lvl 18 ( 27 magic resist) , with high hp from warmog , this amount of magic resistance helps alot against ap champions, it will save you from being killed at one round of their spells , and at the cooldown time of the enemy ap user , you can kill him or at least life steal from him.

doran swords: starting with 3 doran swords , gives a good haelth and damage , besides giving you 12% life steal ( 3% from masteries), if you got some early kills or farmed good , you can get a bf sword after one doran sword, but you will need to get life steal item early , since you will only have 6%.
infinity edge: well...you can`t imagin to play miss fortune without this item.
warmog + atma = this is main idea of this build, the warmog gives a high health and the atma gives armor and critical chance, and combined together with the passive of the atma, it gives nearly 60 damage, so even with two slots for armor and health they still give you the damage of a bloodthirstier, so in other words , you just used 1 slot to give you the 1350 health and 50 armor and 18% critical.
bloodthirstier: gives the life steal needed.
madred: at late game , many champions will switch to get more health items, this will give more damage as the enemy gets more health, also increases the attack speed, and makes you able to kill tanks.

in this build always try to upgrade the w skill first , since there is not much attack speed from items and none from runes.

i usually pick exhaust and flash.
teleport: usually i use teleport when my team doesn`t have many of them , i mean when only 1 player or no one has teleport then u need it , it helps getting items fast and regain health , so you will not lose the lane, and before you teleport you can use the last mana you got against the enemy and deal some damage, recall then teleport and own lane, also it helps defending other lanes if the team were losing - you can`t expect to have a good team each game....ask me about it :(

flash:i never play without it , it helps escaping from ganks , and when you use it well , you can flash to the best place to use her ult, one good ult can change the outcome of the fight to your side.

exhaust: the most annoying champions against mf are the melee ad, like master yi and tryndamere, since they can kill her so fast and they got some skills (q for yi and the ult and e for tryndamere) that let them reach you even if you were in the back line of your team, so if you exhaust him you win.

ignite: i don`t use it , since its range is small and mf got a high range , and you need to stay at the back line of your team in order to make a good use of her abilities.

ghost: this is a good spell you can use combined with her passive , you can reach a high speed and chase anyone.

i will not mention the other spells , since they are not much useful for mf, clarity might be useful for another skill sequence.

advantges:

-high health and armor makes her survives fights alot.
-have a higher chance to use ult at a good place and good time.
-strong early and late game.

disadvantages:

-at the time when you start saving for warmog and before you get atma, all the money you use will not increase damage.
-lower attack speed and movement than the builds that contain phantom dancer.