Hi my name is Marius, i have played league since season 1. My main rank is mid diamond, i also have some smurfs around plat. i stream on my twitch sometimes, basically i just play video games all day.
My twitch is https://www.twitch.tv/mariuskv02 if you are interested

Pros
He has very good Sustain with Transfusion
One of the best Late Game Carries
Amazing cleat and splash damage with Tides of Blood
Good in Teamfights
He doesn't use any mana
He can Escape easy with Sanguine Pool if getting ganked

Cons
Bad early game
easy to gank if your Sanguine Pool is on cd
can be hard to farm early game
not so good before max cdr

Either you go Dark Seal or Doran's Shield first iteam i would recommend Dark Seal the most because you can build it in to Mejai's Soulstealer later in the game, and i fell like that the sustain is almost the same because you can have 3 Health Potion instead of 1 if you go Doran's Shield.
So the reason you wanna get Fiendish Codex and Kindlegem is so that you have or close to max cdr level 10, cdr is very important on vlad. When you have the cdr you can spam you're q, which makes it very hard to kill you in lane because you can just heal after every trade. Fiendish Codex Is build in to a Zhonya's Hourglass or a Banshee's Veil it depends, the Kindlegem is build in to Hextech Rocketbelt. You wil get you're power spike when you have Hextech Rocketbelt, Mejai's Soulstealer, Sorcerer's Shoes and Rabadon's Deathcap and level 13. The last 2 items are very different from game to game. but the options are as follows, Zhonya's Hourglass Liandry's Torment Banshee's Veil Spirit Visage Void Staff Morellonomicon Spellbinder.
If you play vs heavy ap Spirit Visage is very very good because it gives magic resist, heath and 30% more healing. Zhonya's Hourglass is good if you are against heavy ad, and the active can help you a lot in some fights. You can use you're Hemoplague then use the active and get a lot of healing if needed, and you have you're Q up again to heal even more.

Okay so runs is very important, Phase Rush is the best rune on vlad for sure. The reason is that when you activate you're Phase Rush + Nimbus Cloak you can engage in fights or escape from them, Transcendence is for early game cdr its so good on vlad. Gathering Storm is just for ekstra scaling, Magical Footwear is to save 300 gold so you can get you're power spike earlier and the + 10 movement also makes it easier to engage. Cosmic Insight is also just for cdr,
always take +1-10% CDR (lvls 1-18) the cdr is more important then the dmg.
second bonus, is what ever you fell for i like to take +9 Adaptive but you can also get armor or magic resist. third bonus is also different armor vs heavy AD, and magic resist vs heavy AP