Fiora is a very unique AD carry. If you try to play her like any other you will NOT do well! Since she is a melee AD carry that is changing the Meta game, I like to play her bot lane. Since she deals such massive damage early game, it is good to go with someone like Nautilus who can use CC to allow you to put out massive damage, as well as help you burst someone down.

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Duelist Regenerate health after a basic attack
The good thing about this is that it will make you be able to survive after attacking an enemy champion. And in some cases might even save you from an nasty Ignite.

Lunge Dash towards target
An great gap closer and can secure kills if used right.
TIP:
Try getting in range for Lunge so that you can use it a second time instead of using it on a minion to get close to the enemy champion. This will make escape alot harder for them.

Riposte Will block next incoming basic attack.
Not only is it an great item against Auto Attack champions but it also gives you a nice boost in attack damage!
TIP:
Not only does it block Auto Attacks but also attacks like Talon's Noxian Diplomacy and Wukong's Crushing Blow.

Burst of Speed Increases your attack speed
This is what makes Fiora such an incredible champ. At rank 5 it will give you an incredible 120% attack speed boost for 3 seconds!
TIP:
Using Burst of Speed on a snared or stunned champion will maximize your damage output and will give you full movement speed boost.

Blade Waltz Attack one or multiple enemies up to 5 times
This is one of the most incredible things about her. She will deal alot of damage but not only that but it will also proc things like armor reduction and life steal.
TIP:
Getting alot of lifesteal and using your skill when you have low health will return you health!
Caution:
You will end up dealing your last blow on the same target you dealt your first blow to. Be sure you have enough health to survive a couple of turret hits when you are near an turret!

I run Armor penetration Marks and Quints for several reasons.

Her W & E give her lots of damage and attack speed early, the only thing missing is armor pen. Between masteries and runes, you will be dealing true damage to some champions in bottom lane.

Flat Magic Resist Glyphs & flat Armor Seals gives early game sustainability that allows you to deal much more damage while taking a few hits.

Here are some tips for Fiora.

Always have bush control - This will allow you to pop out and last hit minions. If their AD carry targets you, pop your

W to parry it back.
When I fight begins, immediately use your W if under attack, and wait until you begin to attack before using your E, since it is only 3 seconds, you need to make the most of it.
Use your Q to keep up with enemies that decide to flee
Last but not least, once you have your ult, never initiate with it. Use it only when you begin to rapidly lose health, it will heal you just like Warwick's ult. This will force enemies to target other champions while allowing yourself to heal up, and refresh your cooldowns.

PROS:

Tons of Burst Damage
High Sustainability
Start off tanky
Great 1v1 champion

CONS

No CC
If focused with CC,
No quick escape abilities