Honestly man, just don't. Fiora can be sort of fun, but she brings so little to a fight that it's almost laughable. Sure her ult deals nice damage, and she's one of the better duelists, but there are so many better options, and using a melee mid that wasn't specifically designed for mid can be an issue against good mid players. She can be heavily abused, and unfortunately her Parry doesn't help much against someone who's just gonna hit her with abilities instead of auto attacks.
If anything, I would avoid playing her altogether unless you're using her in a team comp that features heavy CC from other members. She might do well in a comp that has a Nami support and a Zac jungle, for instance, but as a champion who has to build almost entirely damage to truly be effective, and lacks significant escape mechanics or CC, she's a very iffy pick for most matchups.