Hi everyone!!!!I bought fiora right after she got released,played very well with her and even got a 1v5 pentakill on my second game with her!!!Was trying builds and this one happened to be really really effective.I've seen people building her like Master yi=>DONT!Fiora is not that good with PD,PD,IE,BT,PD,PD(yi -.-)She has very few weaknesess but she is really really strong champion for 1v1 (yeah she's a duelist)Your Burst of speed gives incredible amount of Attack Speed(120%) so you dont need to build her like tryndanoobs and yi ***s(no offense)

Powerful Cons:
-Insane Lane Sustain with Duelist
-120% AS from the E skill
-Can parry Basic attacks
-Powerful AoE ultimate
-Untargetable while in Blade Waltz

Critical Cons:
-Really Really squishy
-Often targeted first
-Has 3 seconds to do as most dmg as possible

Vampiric Scepter - Why it?
Along with her passive giving her a pretty good amount of lane sustain,this will improve it even further.She becomes extremely good pusher and you will be dominating lanes without any problems at all.
Wriggle's Lantern - Improves your lane sustain even further and gives opportunity to kill almost everyone in 1v1 early game.
The Bloodthirster - Fiora's Ultimate Blade Waltz applies on-hit effects just like Ezreal's Mystic Shot.Using your ultimate at a target on his turret will make you untargatable and with the bloodthirster you will be healing for alot which will give you another edge in killing your enemy at his turret.
The Black Cleaver - It shoud be pretty much mid/late game already and you and your team will be having teamfights.Fiora can initiate teamfights pretty easily with her Blade Waltz and The Black Cleaver will stack it's passive onto targets you hit,which will make it easier for your team to win the teamfight.
Trinity Force - Attack speed?Movement Speed?Health?Mana?Critical Chance?Attack Damage?Slow with every basic attack?Icredible passive(sheen) which will apply another on-hit effect when using your ultimate? Yes please!
Madred's Bloodrazor - Here comes another on-hit item which will help you burst down High HP stackers like Cho'Gath,Volibear,Gankplank(Warmog+atma damn) etc.
And finally Banshee's Veil - Everyone needs atleast 1 defensive item in his build.This item is perfect.Gives you health,mana,MR and an insane passive which will allow you to block spells like Karthus's Requiem and others.Of course if they have Glass AD carries like Master yi,Tryndamere it's better to buy a thornmail to shut them down.

Armor penetration Quintessences and marks=>those will improve your dmg output by alot.Pretty much the best runes for fiora.