It is important to take as the first skill the lunge because you can do the same move twice on the same champion, which in the beginning takes off a huge amount o life (almost 100) and it is also useful because you can chase the ones who are running away. I then max it in second because it deals big damage but its main purpose is to get to the target, not destroy it. This is why i max "burst of speed" because it increases your attack speed so much that it comes to deal tons of damage and it gives you movement speed to catch your opponent when he buys boots before you. Then, the "riposte" skill is maxed in the end because you provide Fiora attack damage in the beginning and her riposte will not be that important because your lifesteal will make you gain the life you would have lost by parrying the attack (maybe not if tryndamere but u will still have the skill, just not maxed)

heal is useful because in the beginning, fiora is squishie and heaving this skill can save her frequently. it is true that it will be less useful in the end game but summoner's spells late game are not valuable too much. the second spell i use is flash to escape any situations when you dotn have your ult. because of of Fiora's insane attack speed, which u max first so you can always catch your prey, life steal becomes her most usefull resource to survive. thats why wriggles comes first after the boots because it is the best overall item : gives attack, armor, lifesteal, free ward and is really easy to build.

then you go for the bloodthirster so when you ult or fight, you regain life so easily.

then, you buy a little bit of life container to be sure not to be destroyed by overpowerful techniques (or ganks) that you wouldnt be able to lifesteal to regain your life. this is the part of the frozen mallet but its principal asset is that your prey will always be at your hand, since u simply use your lunge then basic attack him so his speed gets reduced by 40 % (frozen mallet's passive)

Then the madred's bloodrazor shows up because your attack speed, when you use your burst of speed, will reach around 2,5 / sec. madred's passive is that every basic attack deals 4 % of the ennemy's total health. not only you will lifesteal and do your 4 % during your ult (because fiora's ult applies on-hit effects), you will even slow your pray by 40 %. after 2 seconds of fight, you will have dealt 5 blows of your current AD plus 20 % of his total health as magic. your prey will want to leave but the frozen mallet will cancel his escape. if he flashes, you can use your lunge skill or flash as well.

then another bloodthirster so your attack damage and lifesteal will greatly burst, then the trinity force so every 2 seconds, you will do 150 % of your total AD as physical damage to your ennemy.

Sorry if my english is not perfect, it is not my maternal language :P have a great time playing her !