First guide and I think guides don't need so much info cause you get the skill from playing not from reading.

But for people that can't handle the gameplay without some kind of info, here it is:

Vel'koz = spambot, cause his spells dont cost that much and you can spam that W out of the enemy doing some okey dmg at lvl 3. Always be carefull against the jungler and save your E for knocking him up when he tries to do some ugly stuff against you (wards helps also). Try to farm as much as possible and involve the farming + her***ing at the same time, it aint that hard to aim straight for the AP and farm at the same time, only if he is an passive bastard that just chill around doing some singelspellfarming.

When you hit lvl 4-5 the fun starts imo and you can do alot of dmg cause of Vel'Koz passive truedmg, try hit 3 spells and he drops like butter in the sun, then repeat untill he needs to back or you kill him, and ofc watch out for the jungler.

Well just as much dmg as possible, with the 14 mp and the 45 ap you get as much dmg you can out of the runes with Vel'koz need imo, cause you don't need to be a battleapcaster, just stand on range and let the spells handle the rest.

I personally don't like ignite cause you can use your Teleport to gank bot or top. Bot is always an easykill and ask your botlane for a good ward so you can sneak up behinde and destroy them.
Teleport helps for all situation cause imo, you don't need the ignite cause you got truedmg cause the passive, you can teleport for drake, baron, their jungle buffs etc, yeah you get it. In all situations that you can think of, and when you see people need help.

And flash ofc, works on all champs and should work on Vel'koz aswell, if someon bugging you and getting to close.

I go for as much dmg as possible, enough said.

Pros

+ High dmg in teamfights, good ganks and mobility + cc

Cons

Melts fast, squishy little gangsta

Don't be scared of anything while playing him, do as you like and show them the real dmg that you got. If you get oom, then just b then teleport out on the lane again, you don't often get oom if you farm/her*** right.

Try the combo E+W = DMG. Very good her***combo to drop the hp on your opponent.
Put in the Q+E+W+R combo for ultimate dmg, he can try to run but just follow him with the cursor and finish him of with the ultimate BEAM of destruction.