It depends. Between his only two skillshots, there is A TON of room for failure. If you are exceedingly good with him(My problem when I played him was that I couldn't land my stun and then worry about comboing somebody and then saving my own ass. Veigar is a pretty tough little champ to play imo, but I imagine if you are even a little better than I am at him you will do fine. I was still an asset to my team, being able to almost Q>R the enemy Ahri. Thats another thing, pick him vs ap stacking characters. It really is nice to be able to make a fight 4v3 in seconds. I do not recommend taking him bot as he is easily outlaned. If you are forced to go bot, get an early tear and a revolver. After that just get the normal stuff, deathcap voidstaff, anything that allows you to come closer to oneshotting enemy champions. If you aren't as experienced as him as you'd like I'd highly recommend against getting DFG. It only further complicates things by adding another cooldown you have to wait out and it generally just splits up your damage when you could have spent towards a deathcap. Your targets are going to do regardless of whether you have DFG if you are focusing the right people.
On your build: No, I'm afraid that just won't cut it. Veigar doesn't do near enough damage without items to build like Ryze. That is one of the main reasons he is so difficult, you have to spend 100% into your offense or be relatively useless due to dying so quick. I mean, I GUESS you could build tank veigar and maybe deal enough damage to kill super heavy AP champs, and just be a stun bot, but it feels like you should just pick another character at that point.
I'd say the best you could hope for would be a prospectors and boots start, then head into sorc boots, deathcap, and maybe a rylais to help with that extreme squishy-ness.