Go this ****: Marks: Flat AD, Seals: Flat armor or scaling HP, Glyphs: 3 scaling and 6 flat CDR. Quints: 2 attack speed and 1 AD.
Flat AD marks are pretty self-explanatory, you need the nice damage, and it'll help you farm quite a bit.
The armor seals are usefull against AD opponents, but if you do not wanna commit that much to counter AD champs, you can always go the scaling HP, being fine against both AP and AD champs.
3 scaling glyphs for 5% and 6 flat for 5%, leaving you with 10% later in the game.
The AD quint is just for the damage, meanwhile the attack speed quint will help you do fast trades and proc vitals.
For masteries, there are several options, but my favorite is the fervor one, since it'll help you duel quite a bit.
Go 18/0/12, like this:
Fury, Feast, Natural Talent, Bounty Hunter, Battering Blows, Fervor.
Unyielding, Tough Skin, Runic Armor and Insight.
Your skill sequence can go 2 ways: Q>E>W or Q>W>E (and ofcourse ult whenever you can). Most of the time, Q>E>W is best, so if you're unsure, go this one. If you're in a trading/fighting lane, go E. If you're playing against a laner/jungler with high CC, like Gragas, go Q>W>E.
Start Corrupting Potion or Dorans Blade, depending on you wanting to all in or trade. Corrupting is often best. Try to quickly get a Tiamat or Phage, Tiamat if you're really ahead, and Phage if you need extra help to proc the vitals/survive. Upgrade to either Black Cleaver (against tanks or if you're even/behind) or Trinity (if you're against squishies and you're snowballing hard) and a Ravenous Hydra. Then just choose between Dead Man's, Randuin's, Warmog's, Spirit Visage and GA. Get Warmog's, Dead Man's or Randuin's against full AD. Also just get some boots whenever you have some extra gold. Choose between: Ninja Tabi, Boot's of Swiftness or Mercury's.
What to do
What you need to focus on during the game is splitting, if you get ahead, well done. That's what you need to happen. Fiora excells at 1v1/2/3 situations. Try splitting, and if they send a jungler or something up to kill you, tell your team to go for objectives. Later in the game, or if you get 2 towers in top, go join up with your team. In fights either you try to burst a squishy or you ult the tank to help your team deal with them. Your average Fiora trading combo will be: Q-AA-E-AA-W (if he doesn't have a skill you really need to block). To proc vitals go E-walk-Q-walk. The extra move speed from your ult will really help you proccing the vitals.