Yo, fellas. I'm just a regular player like you guys and checked Fiona builds guides last night and noticed there's no real guides that stand out in detail explanation that's necessary for a new champion to get picked up and actually learn her even though its hard at start, Anyways, without further adeo, hope you enjoy and learn from this guide of mine. ^^

Runes are pretty self explained, She needs that lil extra dmg from quints, armor seals, magic resist per level glyphs, and the most important: armor penetration marks, as these benefit her most at the lane as she is rather squishy at start and hard to handle at early game considering she cant really rally before 6lvl

Masteries are pretty regular ad damage character masteries, almost same as usual ad carry masteries, Good for me atleast.

Becouse you wanna last at lane and actually get some farm and have upper hand versus autoattack champions you want to go 5 health potions and a cloth armor, after that boots, vampiric scepter, long sword, (If possible go madreds/wriggle). After that you want some survival right and some spanky to improve junglers chances of getting a successful gank at your lane, get Phage, yes, Phage. Finish Mercuries, buy a second vampiric scepter, Then its up to you to either finish Frozen Mallet or do it after Bloodthirster, I personally just go Bloodthirster, in rare occasions you can go Frozen Mallet first if youre the only ''bruiser/tanky'' character in the team. After you've got your Frozen Mallet and Bloodthirster, Aim for Guardian angel and Banshee's veil, I mean, your own damage from Riposte Passive, wriggle, Bloodthirster and Frozen Mallet is just what you need to make enemy team be ripped to shreds by your combos in teamfights, Incase the game goes on longer, you can sell wriggle for a second Bloodthirster / Infinity Edge / Atma's impaler (If enemy team has heavy ad dps, If they get Last Whisper, dont bother, just go either Bloodthirster or Infinity Edge)

You really want to level up your Burst of Speed as fast as possible, as its your real bread and butter skill to get some fatal harrassment done to get your kills easier, Riposte just becouse of the AD Passive and the parry ability. Put one point in lunge at 3lvl or 4lvl, then just level it at end to 5.

Flash for escapes/Flash for a sure kill or a tower dive

Ignite for just the lil extra dmg that you need early to pull off kills and endgame it totally rocks the enemy carrys lifesteal with 50%, and yes, It matters.

In ranked play you want to be careful of being counterpicked, If you want to be sure, just swap with another summoner to avoid counterpicking, Get a couple wards early as you're an easy target for a kill, considering you dont get any movement speed from burst of speed unless you hit an enemy. I'd say just sit back, farm, poke and lunge in and out with burst of speed and riposte(if necessary). In teamfights, you want to either iniate if the team is really near you and coming in the moment you ultimate or catch a opponent offguard.

With Riposte passive dmg and a wriggle last hits will just flow to you.

Jungling route is rather easy on Fiora, you can start a blue with ease.

Then head to wolf camp, wraiths, Red buff, duo golems, Look if theres a chance to gank top lane or mid, If not, just recall or if you lack some gold get wolves again.

Even she is called a Duelist, She does need a team around her, as she's easily targetable mid/early game, in endgame you can feel free to iniate, overextend a bit if your team/teammate is near, As you got that beast damage, survival items, Nobody really wants to 1vs1 or 2vs1 you at end game, They will need more than 2 or 3 to get you down.

Olaf is a true beast versus fiora, because all he needs is to poke with his Reckless Strike and you will be to scared to go too close and he still has Undertow and ultimate and that imba lifesteal

Irelia is just another beast to face, Depending on the goodness of the irelia you can either be facerolled totally or just the opposite.

Riven, I would say she aint too hard to handle, like Olaf or Irelia, but she still has her Q combo and stun+shield that makes her really a worthy opponent, and not forgetting her ultimate as it improves her Q dmg and the ult deals a lot of damage if youre hit low.