Fiora is a strong but somewhat squishy until built melee that is a late game massacre.

Lunge-
The ability name explains its self, I pick it up first and continue "WAY" later because it's extra range. You have two landing hits, it does additional damage, but your next 2 buffs are much more helpful.
How do I use "Lunge"?
I use it to get to the enemy that's faster, escaping, or even the appropriate turret dive.
Riptose-
Riptose is a great ability for going against harassing champs because it parries and does damage back to a squishy range, this is a amazing ability for escape routes when used correctly. Also it is a better one for melee or one on one fighting because of how clean cut you get out of it. If used correctly Fiora can finish off there DPS/Tank and get your team an Ace. To add on to your opponents wound it does extra damage permanently.
How do I use it?
I use it aggressively against ranged who are squishy so I can get kill or anytime when I'm running away. REMEMBER THIS MAKES IT SO YOUR OPPONENTS STUNS DON'T WORK FOR ON THE LANDING AND YOU TAKE NO DAMAGE. It is amazing going against Ashe(for exp.), but not Fiddles(for exp.) because Ashes ultimate will hit when you have the parry and it will do no damage hurt her and you will escape or kill her but Fiddles will land his fear you get silenced by the crow and you are done.
Burst of Speed-
This basically just helps movement speed and attack speed. Pretty simple you can use it when needed be cautious of when you do.
How do I use it?
I use it on turret grabbing or when I am bout to die and I am on max cool down and lay off the combo that goes R(Blade Waltz),W(Riptose),E(Burst of Speed),Q(Lunge(1)),Q(Lunge(2)).
Blade Waltz-
This is your ultimate as you could tell. You want to use this with caution because the cooldown is not pleasant to wait for. But yet is worth it.
Ho do I use it?
I use this at caution but when I do its when it's a 1v2,2v3,3v4,4v5,5v5. Or to get an Ace to get game. This ability works as Alpha Strike on Master Yi but does not hit minions for 5 MAJOR hits that they can't escape sounds good to me.

Pros
Fiora is a high damage output and deals more then A LOT of melee champions could attempt.
Cons
She has low mana early game and even mid game and when feared, stunned or anything then put in a ruff situation.