Vlad is pretty fun, but max his Q first, its his bread and butter. Items that give both AP and health are great for him thanks to his passive, so make sure you buy him a haunting guise and a rylai's scepter on him. I was playing him on mid but then my stupid brother messed up the network because he's derp tier. And now the servers are busy again, ffff.
E is usualy the last spell you level as him, it consumes too much HP early on, I usualy just get 1 level to help with minion farming. His Q is a single target nuke thats spammable at level 5 (3 second cooldown), hurts quite a bit and gives you health. It gives more health then you use to cast it, so you basicaly have a free one target minor nuke that heals you, awesome for mid lane harrassment. His W is godlike, make sure you pick one level of it early, and max it right after Q. Don't use it to harrass though, ever, people avoid attacking vlad because they know he can just pool away, if you waste it a smart player will know its down (cooldown is fairly high) and raep you, only use it offensively to farm minions when you're sure there'sn obody around for the next 12 or so seconds, and to kill people when you're absolutely sure you can kill them and that you need pool for it.
Vlad's E is an extra instant multitarget nuke that's great for minion farming and giving you some extra firepower, but its range is shorter then Q's, and you'll rarely get a chance to use it effectively on early game, it just costs too much HP to cast it early on, so don't spam it or you'll end up dead before you notice it. His E is more for mid-late game, and even then you won't spam it that much. Its still extra firepower so make sure you use it when something's in range.
His ultimate is to kill low health people in mid, otherwise leave it for teamfights, never use it against a single target out of laning phase, its an incredible spell if your team knows how to take advantage of it.
My build is usualy. Q > E > Q > W > Q > R > Q > W > Q > W and so on, getting R whenever possible and maxing Q first. I'm tempted to buy ionian boots of lucidity on him. As for items, if you're confortable on mid, you might wanna go for haunting guise on your first trip back, then buy some boots. After that its your choice, but I like to pick rylai's as my third item, followed by deathcap and void staff.