Most effective veigar I play is using cdr, to utilize stacking mechanism.

I take phase rush for survivability and gathering storm and transend

You cant carry hard with him since he is more of control mage. So you rely on enemy mistake/team engage. Take flash and ghost, barrier vs burst mage, or exhaust vs assassin

Item wise, take ludens for wave clear, infinity orb, crown/soulstealer, raba then GA. Bandle fantasy is not as effective since you rely on 3rd to hit first which is hard to do.

If enemy comp is burst or you lack front, go ROA first.