Whats up, this is my first build so criticism is acceptable also i don't know how to make this build looking as good as the others so don't judge :)

Pro's

Immense nuking power
One of the most annoying mages according to the enemies
Underrated meaning that less people will use this guy
He's a yordle
Has stun
Great farmer

Con's

One of the most annoying mage if your fighting him
Squishy
Weak early game
Event Horizon is your only defense
Get focused at team fights
Bad matchup against Le Blanc because of her silence
Long cool downs

My masteries for veigar are 21-0-9 i did this masteries because simply veigar is a very squishy champion and sometimes gets focused for his immense nuking power, I put defense because of this fact

For runes i put flat magic penetration marks, this is because it helps improve the damage that veigar use, it is also very helpful against tanks but champions that build up a lot of magic resist are champions you should try to avoid without an ally next to you. For seals i used armor and magic resist just to boost viegar's defense as i said earlier on hes one of the squishy mages.
For glyphs i used flat ability powers again this will help you nuke down enemies and add more ap to your stats (useful early games)

i start of with Dorans rings to cover early game damage and mana regeneration, and some health. This is my PLAN if you are doing well in your lane you get another dorans ring,if not get boots second then get dorans ring. I then rush rabadons deathcap, why? because you do some damage to the enemies nearly enough damage to bring them down near half health.( Im being honest with you guys because other people say you do lots of damage with it at start but not as much so im warning you) The next four items is up to you guys. Heres a tip: once you get archangel start whilst your in your base spam all of your abilities and it will activate its passive, once when i was in a game an enemy Karthus had 5 arch angels and one mobility boots, he had at least 1000+ ap, so if you want spam on archangels.

Again as i said i don't know how to add pictures so just bear with me.

Here is veigars COMBO REMEMBER THIS WELL E > W > Q > Ri cannot stress how much that combo is very important that COMBO is, it so important that you cant kill a full health enemy without it, unless you have crazy damage that you only need one ability to kill like Q R W.
Back to ability sequence always always pick Baleful Strike first this is because your main objective at early games are to last hit minions because of Baleful Strikes passive which is that if you kill an enemy with it you get 1 ability power point if minions, if its champions then 2-5 depending how much you upgrade it, if you can harass enemy champs at early but i would focus more in last hit. Second get your stun and now you can harass enemies it can also be a lifesaver for early ganks eg. junglers. Thirdly get your Dark Matter now you can do some of your combo and hope your enemy feel threatened, after you should max Baleful Strike first then Event Horizon after Dark Matter and lastly your ultimate Primordial Burst whenever you can.

i use ignite because its very useful for your combo it gives additional damage not much but hear this out your opponent wont notice it, this is because he just survived your full combo and obviously he will run away it will take them a few 1-2 seconds till they realized they are ignited and that's very important. You should really use ignite after you sue Dark Matter because your stun has a good range so after you stun unleashed Dark Matter immediately try and catch up and ignite him then do the rest of the combo Hint: this will only take a few steps just enough to be in range with your Q and R skill. My second summoner spell is ghost now theres a lot of argument about which to pick Flash or Ghost to me i use ghost for mostly mages but thats just if you want use Flash it doesnt change the fact that it can be used to catch up to enemies or running away from enemies.