I build Miss Fortune with Armor and Magic Resist marks; Health, Armor, and Magic Resist runes; Health glyphs, and Health Quintessences making her very hard to kill. I add a few mana runes so i can use Make it Rain more often.

I use a 21/9/0 build because Miss Fortune is still a high dps character. Making sure to get damage and some ability power, i also go with dodge chance and some armor/magic resist.

I start out with the Doran's Blade because the damage and lifesteal are important.
I then move to Warmog's Armor because the massive amount of health makes Fortune really hard to take down
The Tiamat could be swapped out wit another item maybe the Black Cleaver, i like it because the splash damage helps take out minions.
The Bloodthirster comes in handy due to its high damage and lifesteal to help in fights.
I then proceed with Boots of Mobility allowing Fortune to zip across the map with ease.
The Gunblade comes next as it is just good to have, the ability power and attack damage help alot.
I end the game with the Infinity Edge because we always need more attack damage.

I usually go with Clarity due to Miss Fortunes lack of mana.
And Flash is always just a good spell to have.
Exhaust and Cleanse might be good alternatives to have if you don't like the others
I wouldn't get Ghost or Teleport as Miss Fortune is fast enough she dosent really need them.