Welcome to my Vi guide! This is my first guide so please feel free to criticize and help out! I'll add more to the guide once i test out some other items.

Pros

Strong early
Great escape (with Vault Breaker)
Decent Harass (with Relentless Force)
Tanky

Cons

Low attack speed (though it does get boosted with Denting Blows)
Can go OoM early game (this has happened quite a bit to me but it really depends on who you are fighting)

Recommended Spells

Flash (great if Vault Breaker is on CD and need to close in or get away)
Ignite (great if enemy is trying to escape and can't get in range for Vault Breaker/ Relentless Force)


Other Useful Spells

Exhaust (slow down the enemy to get in range for Relentless Force)
Ghost (speed to get in range for Vault Breaker/ Relentless Force)
Heal (self explanatory)

Reasons i chose selected items.

Black Cleaver - Boosting Vi's AD and health is great! Toss in some CDR and armor reducing debuff and Vi can mow through just about any champion!

Frozen Mallet - AD and Health is great...and slowing enemies movement speed is amazing! This item give you survivability, more damage, and a great gap closer.

Bloodthirster - A gain in AD while adding life steal and a stacking buff that grants life steal and damage is a great thing. Keeping Vi's damage high while keeping her health up.

Mercury's Treads - I chose Merc simply for the MR. If you want to you can purchase
Berserker's Greaves for the attack speed or Ninja Tabi for the armor boost.

Wit's End - Boost in attack speed and MR and a stacking buff adding magic damage and MR. This item keeps you safe from AP types while boosting DPS.

Maw of Malmortius - This item is great! Boosting AD and MR while also stacking a bonus damage buff and bubbling you.

This section will feature scores for people who have used this build.

To Vi, every problem is just another brick wall to punch through with her gigantic hextech gauntlets. Though she grew up on the wrong side of the law, Vi now uses her criminal know-how to serve Piltover's police force. Vi's brash attitude, abrasive humor, and blatant refusal to follow orders can often infuriate her by-the-books partner, Caitlyn. But even the sheriff of Piltover cannot deny that Vi is an invaluable asset in the fight against crime.
As a child growing up in the lawless outskirts of Piltover, Vi learned to rob and cheat to get by. Stealing and stripping hextech hardware gave her the skills of a master mechanic, while life on the streets taught her self-reliance. When she was six, a ragtag group of criminals took a shine to the young delinquent and brought her into their fold. By the time Vi was eleven, she had become a seasoned accomplice, and she relished the thrill of every heist.
Vi's attitude changed when a raid on a mining facility went bad. She was forced to decide between fleeing with her crew or trying to save the innocent mine workers from a collapsed tunnel. Vi chose to play the hero. While searching for a way to free the mine workers from the rubble, she discovered a damaged robotic mining rig. Improvising, she wrenched off its huge fists and modified them into makeshift hextech gauntlets. Fitting the heavy weapons to her tiny hands, the young girl flexed her arm and threw a powered punch at the rubble. The force of the blow blasted away the rock. With the workers free to escape, Vi fled the scene.

After that job gone wrong, Vi severed her connection to the crew. She returned to a life of solitary crime, but stole only from other criminals. As the years went by, Vi modified and improved her hextech fists, allowing her to bust up heists and snatch loot with ease. Eventually, word of her notoriety reached Caitlyn, the famed Sheriff of Piltover. Rather than seek Vi's arrest, Caitlyn offered the criminal a way to pay her debt to society: work for the law in Piltover. Vi laughed. To her, a job that let her beat up crooks without forcing her to run from the cops sounded perfect. She immediately accepted. Caitlyn now struggles to keep Vi in line, and Vi treats Caitlyn's orders as mere suggestions, but when they work together, they are feared by all lawbreakers in Piltover.