Marks: flat AD, ArPen or AS
Glyph: scaling MR
Quints: flat AD or AS
Ghost is mandatory, it's far superior to Flash because there are way less walls to flash over than in SR. Smite is mandatory vs good teams. You'll need it for clear speed and security for your early and vilemaw.
Masteries are 21/9/0 or 9/21/0 depending on matchup. I value AS or CDR over havoc. Though Skin/Bladed Armor can be swapped with MR or armor.
There are no essential items. Vi has an innate AS and ArmorPen boost and a shield. This scales best with ad, lifeleech and resists. You need to know whether to build more tanky or more dmg. Vi can still do a decent amount of dmg without dmg items but she scales harder than most tanky dps. Rush BotRK or build Bilgewater Cutlass+Giants Belt first. Everyone knows that lifesteal scales well with ad/attackspeed/crit but many neclegt that it also scales with resists(but not with health). 100 life leeched are essentially 150 life if you have 50% more resists.
BotRK+ stacking resists will make you an excellent duelist. Use Q+ult+botrk active+ghost to obliterate any squishy. Tankier champions mostly can't win outright an 1v1 vs you. Only problematic champs are like Jax, Aatrox, Singed. You should be able to win vs champs like Tryn or Yi unless they are extremely fed or very late.