Pros

OP burst damage
Has some CC with his E
Teams up well with other CC champs

Cons

Really squishy in early game
Is mana depending
Needs very expensive items

The skill sequence is very easy:

E W Q (R, if enemy isn't dead already)

Keep farming with your Q for great amounts of AP

Veigar teams up really good with CC champs like Xin Zhao, Alistar or Blitzcrank. You can stun them and they pull, push or knock him up in the air.

This was my veigar guide, i hope you will win more games with him now. Enjoy trying it out!