Hey! This is my second guide and I chose my main character :)

Vladimir: your enemies' worst nightmare in mid lane :P

Since Vladimir has a very good source, you can use it since beggining, so I chose:

9x Greater Mark of Magic Penetration: The magic penetration you need to pwn your enemy :P
9x Greater Seal of Ability Power,
9x Greater Glyph of Ability Power,
3x Greater Quintessence of Ability Power: the AP you need to put your source active ;)

You can replace Greater Seal of Ability Power for Greater Seal of Health or Greater Quintessence of Ability Power for Greater Quintessence of Health, that's up to you :D

Vladimir is a great begginer, so try to use this for your advantage :D

For masteries I use the standard mage tree: 9/0/21

The points in Utility are quite good; the AP and CDR will help you in Transfusion mostly :D
The points in Offense will give you a boost AP and Magic Penetration.

For my item build I choose AP and Health because of his source.

So I start with Amplifying Tome and an Health Potion. Vlad doesn't have mana, so this items will keep you laning forever. When I can, I buy Hextech Revolver for AP boost and some Spell Vamp; this two bonus will keep your Transfusion relatively annoying <.<'

I don't get Boots too early, because Sanguine Pool will keep yourself safe, but try to get it for some Movement Speed. Don't upgrade this to Ionian Boots of Lucidity; it's more useful getting Will of the Ancients first and then Ionian Boots of Lucidity.

Now it's time to be even more annoying :D Buy Giant's Belt and if you have enough gold get Blasting Wand. AP + HP = HP + AP :P So simple as that. Then finish your Rylai's Crystal Scepter and start making Rabadon's Deathcap. Try to end with a Void Staff or Abyssal Mask.

For summoner spells I use Flash and Ignite.

Flash: Pretty good to chase or to run away.
Ignite: Great combo with Transfusion + Hemoplague = DEAD

Alternatives:

Exhaust: Same as Flash, but the Magic Resistance and Armor reduce are quite good to deal a good amount of damage.

I think this is the essential to play Vladimir :)

The AP and HP boost in runes can lead to a good begining to him :D
The item build is quite good to get a Legendary Vlad :P

Waiting your feedback :D