*EDITS*
Fixed item build around, made Will of the Ancients earlier while delaying the Rabadon. Got rid of the Void Staff and replaced it with Zhonya's Hourglass. Added in Elixir of Brilliance.

Vladimir is an AP carry, and he is a good one if played correctly. Now many people say that Vlad is really bad and I disagree. Although he is definitely a shadow of his former self, he is definitely still strong and viable. His early game is extremely weak and fragile and should be played with caution. After he reaches level 7-9, he is going to dominate laning and at getting creep kills. His late game is extremely strong, and with a good amount of creep kills and items, your AP will be extremely high along with his health because of his passive. His roll in team fights is to stay close to the enemies to use his tides of blood and using transfusion to stay healthy. Now time to teach you about the League's Crimson reaper.

Pro

-Good survivability
-Good late game
-Good farming
-Good damage
-No need to worry about mana costs

Con

-A weak early game
-May be outshined by other AP carries.
-His skills use health which may be the death of you if not managed correctly

Magic Penetration Marks because these runes are essential to any AP caster to do more damage.
Health/lvl seals because they are much better than flat health runes, giving more health at level 5 than flat runes, thus more AP.
Now for the Glyphsd, you can go two ways: AP/lvl glyphs or CDR glyphs. The AP/lvl glyphs are good for the extra AP, but due to recent nerfs to cooldowns, cooldown runes might also be viable.
Health quints are always good for champions, but even better for Vlad because of the passive. It also helps because it will give him an additional 78 health for his weak early game.

I go with the standard caster runes, getting the extra AP, cooldown, and magic penetration masteries in offense.
I get nothing in defense because you are an AP carry, not a tank.
I get almost all the masteries that do not include mana in utlility, allowing him to get extra experience, gold, longer buff duration, increased speed, and decreased summoner spell cooldowns.

I start with Amplifying Tome and a health pot because he doesn't need any mana regen, ruling out the Doran Ring. The Amplifying Tome can also build into the Hextech Revolver.

For boots, I would either get either Sorcerer shoes if they lack any crowd control or Mercury Treads if they do have crowd control. People are wondering why I am getting Mercury Treads rather than Sorcerer's Shoes. The reason is because that is how I play Vlad in the beginning stages. I play extremely safe and want to make sure that I can stay safe in lane and Mercury Treads can help me with that. It offers the +24 Magic Resist as well as the tenacity to reduce cc.

The Hextech Revolver is essential for Vlad, allowing for better healing and for his Tides of Blood to counteract its cost.

A Rylai's Crystal Scepter is a great item for Vlad because it gives him better chasing power allowing him to slow enemies (this will pretty much be his only form of cc next to his pool), as well as giving him great HP and AP. This item synergizes incredibly well with his passive, giving him 92.5 AP rather than 80 AP and giving him 644 HP rather than 500 HP.

Rabadon's Death Cap is always a good item for any AP caster. It works well with Vlad because the extra 30% from Rabadon's passive effects Vlad's health passive.

A Will of the Ancients is a good item for Vlad, as well as the rest of the team. The increase from 40 AP to 80 AP and the increase from 15% Spell Vamp to 25% Spell Vamp is a lot. As well as the fact that everyone around you gets 25% Spell Vamp and 30 AP makes it even better. To top it all off, it only costs 900 gold to upgrade. That is an incredible deal.

(Side note: How does a revolver turn into a book?)

I think these first 4 items are essential for Vlad, but these next two can be varied, depending on what the enemy team is.

If the enemy team is building a lot of Magic Resist, you should build a Void Staff to cut through 40% of that Magic Resist.

If the enemy team is heavy on AP, while not getting too much Magic Resist, then get an Abyssal Sceptor. It's great for the AP, magic resist, and the Magic Penetration aura which is good because of your close proximity to the enemies in team fights. It only costs 355 more than a Void Staff and it can do A LOT more. It gives the same amount of AP but the Abyssal Scepter has 57+ Magic Resist. If there is little to no Magic Resist, then the 20 Magic Pen per enemy will be helpful to you and your teammates that are also AP.

If the enemy is heavy on AD, get a Zhonya's Hourglass. It gives a lot of AP, a lot of Armor, and the Active on the weapon is just another plus in case you get in a bad situation. You can use the active if you are in a bad situation and are waiting for cooldowns. I love situations where I am in a close fight and my pool is not off cooldown yet, so I pop the active, wait for pool to come back, and finish off opponents once I am out of stasis.

If you go back to you pool and you have around 400 leftover after buying everything, buy some more pots, wards, and something that is important is the Elixir of Brilliance. Due to some recent cooldown nerfs, the elixir can really help you out, only costing 250 while giving 20-40 AP (depending on level) and 10% cooldown reduction.

For skill sequences, I try to max my q first because this is Vlad's bread and butter skill. This is what gives Vlad his incredible laning power and laning presence. This is what makes farming so easy with Vlad. This is what gives Vlad his survivability in lane.
The next skill to max was w. The only reason why I would do that is to lower the cooldown. This skill is really great for getting away and for getting inside the team and slowing them.
I max e last not because it is the worst spell, but because I want to prioritize q and w first. His e is actually ridiculously strong in team fights, being an AOE spell that can do around 400 damage.
Now to his ultimate. I think that this is one of the strongest ultimates in the game. It makes all the people affected have the damage done to them increased by 14%. Now that does not seem like much, but 14% is actually a helluva lot of damage. The extra damage at the end of the duration just serves as finishers to anyone who escapes.

I usually get Ghost and Ignite.
Ghost is good because it can allow for fast initiations and also fast escapes. An example of using it for initiations is if the tank goes in, you should ghost in, throw your ulti, use your e, and try to pool into the enemy team. An example of using it to escape is to activate ghost and then use w. It is important to ghost before w because it makes the pool faster. Here is something that is not included in the tooltip of the w skill, the w has a speed boost in the beginning of it.

Ignite is good for different reasons. It reduces the healing of an enemy so it is best to use on an enemy that tends to heal, such as fiddle, or another vlad. Another good thing with ignite is that the damage over time is actually effected by his ulti. It is good to ulti, ignite, and then spam the rest of his skills.

What he does during team fights is stay in there for as long as possible, trying to hit a majority of the people with your ulti and e. He picks off weaker enemies with his q and slows anyone else with his w. In team fights, because all of the skills use health, you need to make sure you stay healthy with your q. It is best to go in after the tank initiates and throw down your ultimate to hit as many enemies as possible and then let your teammates tear apart the enemies utilizing the extra 14% damage, while you are spamming your e and q. If your team does not have a tank, then you can initiate the fight. Throw down your ultimate and let your teammates fight the other enemies while you are spamming e and q in the midst of it. An important thing to consider before going into a fight is making sure that your e is at full stacks when going in. It is better to go in at full stacks than at no stacks at all. The difference in damage is a lot. An e at full stacks does about 244% more damage than an e at no stacks.

Now this is what I love about Vladimir. His ability to farm is extremely easy. Last hits are easy to accomplish with his q and e, and even with his auto-attack. In the beginning levels, the cooldowns for q is extremely high, starting at 12 seconds at level 1. Even with the high cooldowns, just try to use your q as much as possible to get last hits on minions. Make sure you do not push hard early level. It is better for the minions to be at your turret than the other way around. Now because of Vlad's weak early game, the minions will most likely be pushed up to your own turret. Now most people may find this annoying because the turret can kill all of the minions, but Vlad can actually farm with the turret really well. After you hit level 5, your farming becomes easier. Your q is on a shorter cooldown and your e is great at farming a large amount of creeps. What I tend to look for is one or two minions that are extremely low and another one close by that is about less than half health. I go in, e and pick up the low HP creeps and then I quickly q the one that was around with less than half health. If you are lucky, the amount of low ones will be more than two and can even pick up 3 or more with e. If you see any enemy creep pile ups, try to go to them and get rid of them. If you just go in, you can nearly take out the whole pile up with two e's. Now here is something important. DO NOT FARM WITH W! His w costs 20% of his health and the damage and lifesteal that is done does not counteract the cost. It also puts you in a dangerous position as your go to escape spell is on cooldown.

Now this is just a side note and does not apply to only Vlad, but when in laning phase, try to prioritize killing the cannon/siege minion in the wave. It gives the most gold and it only comes once every three waves. I tend to save up my q and use it on a low siege minion.

Vlad is a great pick for an AP carry. He does a great amount of damage and is valuable to the team. His q allows for great sustain and keeping his health up. His w is great for escapes as well as getting into the fight. His e is great in team fights doing good aoe damage. His ultimate is amazing for teamfights allowing other teammates to do more damage. He is an amazing pick and even though he has gone through many nerfs, he is still a strong pick.