If you check the abilities of this hero you can point 3 things.

1) Vladimir has a passive spell giving benefits from increased health and increased ability power. So you need to max those two stats.

2) Vladimir doesn't need mana but instead life to cast his spells so you can skip all the mana items and go for life and regen items

3)Considering you have enough life to cast your spells, the last limitation is cooldown so you need to reduce those as much as possible.

This is not a guide, just a build. The items proposed, runes and skills sequence are all in synergy to maximise the pros of Vladimir. Tell me if it improves him a lot...
Anyway, the items will transform Vlad in a real tank, capable of casting quite fast, draining life from ennemies and farming a lot with the sanguine pool. Tides of blood is expensive in life so wait the end of the game to maximise it when your life will be sufficient. The little "plus" is the frozen effect: Rilay will slow you targets and Randuin will slow people attacking you so your team mates will have an easy time killing the remaining ennemy heroes...
For the remaining items, I suggest to buy again one of the major items: for life and cooldown: Randuin or spirit visage (cheaper), for life and ability power: Rilay. If you need more cooldown than penetration you can buy the "reduc cooldwon"boots (I forgot the name...) instead of sorcerer shoes

Enjoy !!