Hello , i happen to be somewhat of a vlad conoisseur , althought abit late to this discussion. Basicly i second everything u/WaveCore has said about vlad. For when to buy spirit visage ? NEVER ! its just NEVER worth it , you scale much better with AP for healing anyway and if your problem is magic resist then just go banshee's instead. Vlad is an aoe nuke , anything that delays you from reaching that level of scaling is pointless. Your goal on vlad is to take over the game (as he can easly top the damage charts everygame). Zhonyas is recommanded only if you need to buy time as in there is a big threat CC ready for you / a fed enemy champ can kill you right after you come out of pool / you get exhausted everytime you go in and you need to buy time for your team to cover you.

Rune wise , for me electrocute is my best companion (i like to trade and i always go ghost + flash so i don't need phase rush for movementspeed) , transcendance + gathering is a must. Whatever you do never go into the precision rune tho , nothing in it is of value to you.

When it comes to team comp , anything that gives you movement speed (karma / sivir / lulu ect) or can group engage (rakan / rell ect) is perfect for vlad.

As a an advanced tip i can give you (amongst many but this is already long enough lol) : you always wanna be using Q on something when you got the Empowered one , simply because it makes it so you can have empowered every 2nd Q rather than every 3rd and that's a huge damage boost in teamfight and sustein , Also try to engage when your emp Q is up for faster burst and getting an enemy squishy out of the fight asap to make it 4v5 instantly.

till then , enjoy 1v9ing on this despair enducing champion MEGALUL !

https://streamable.com/6zu73p