Across 1,456 ranked games on patch 16.21 in Master and above, Fiora mains win 54.1% of their games in the top lane.
Their most common build appears in 40.2% of those games and wins 53.1% of its 586 games.
It starts 
Doran's Blade and 
Health Potion, completes 
Ravenous Hydra, 
Eclipse, 
Death's Dance and 
Endless Hunger in that order, and takes 
Plated Steelcaps.
Three other builds are played often enough in the top lane to be measured on their own.
In the top lane, Fiora mains fare best against 
Olaf (won 70.4% of 27 games), 
Riven (won 73.7% of 19 games) and 
Ambessa (won 60.8% of 51 games).
Their hardest matchups, the champions that counter Fiora, are 
Pantheon (won 37.5% of 32 games), 
Shen (won 35.3% of 17 games) and 
Darius (won 44.2% of 43 games).