Hi summoner!
I'm here to introduce the great mage Nunu!
In this guide, I'm going to teach you how to build a spectacular sorcerer. Some people likes to make him a tank or off tank, but I don't think you can undervalue his ult. You can easily get 2500+ damage with that.

I really like that kind of runes. It's just perfect for every mage at early game combined with doran's ring. The spell penetration gonna make you a vary annoying person to lane against. :D

Some truth needed to be put here: I'VE NEVER COMPLETED ANY BUILD WITH NUNU!! The game always finish too early for that.
You are able to make any changes you need in the game as you wish, but I really think 3 rings, Rabadon's Deathcap and zhonya's hourglasses gonna make you indestructible. I'm gonna explain that at skill sequence (next topic).

In early game, is necessary you use ice blast any time you can. With that, you are going to keep your enemies low healthy, and keep you save from the most of chasing they can do.
Try to keep your allies buffed with blood boil, mainly if they are ad carry. If you are solo top, you have the option of do that on minions, but i don't recommend that if you want to keep your mana high enough if you need to use ice blast without hitting enemies.
And consume, like everyone knows, is here to make you heal the most part of damage you take from ranged enemies.
About ultimate, if you have chance to, use that in the bushes when your enemies is approaching of you, they won't see what you are doing and the only tip they get is the slow. By the way, if you know somebody is in the bushes, just use that in some place you have a guest they won't be able to run out of it.
In team fights, try to use your ult as early as you can, then your partners have health enough to protect you from all of them. After that use Zhonya's to keep you alive even losing lots of health. With ice blast and ignite you are going to keep yourself fed and raping tons of kills.

Flash: can be used to jump onto your enemies and use your ult right where they are, also can be used if you need to run out of fights after using your ult.
Ignite: as I said, flash is highly used to keep you fed when your spells are on cooldown or enemies are low health after your ult.