@abboz, Good point sir. Many people agree with you and prefer to max Q first to capitalize on in-lane poking. Although I throw my Q out quite frequently in lane, my general philosophy is to bait them into going all-in. Once they do that, I land an E on both of them and lay down my W to hit both stacks and pop my passive. This combo alone (when W is maxxed first) does about half of their health, making it an easy cleanup for my ADC with me playing a more passive role at this point.

However, I have seen people max Q and make good use of it. Ultimately, its a playstyle difference.

Good comment on matchup information, this is definitely something I look into adding to the guide in the future.

Thanks for the feedback!

"I start with Plasma Fission, but max Void Rift first for a couple reasons. Plasma Fission is more appropriate level 1 since it has a much longer range and also applies a slow. However, I max Void Rift because it is often much easier to land than Plasma Fission, does more damage than Plasma Fission if you place it properly, AND has the potential to apply two stacks of Organic Deconstruction to multiple enemies. Next, get Tectonic Disruption if the enemy lane is pushing/harassing a bit; or Void Rift if you are pushing their lane and want some additional harass. Max Plasma Fission second followed by Tectonic Disruption."

I don't like how you max your w first. I think it's more viable to max your q first because of the mana drain on you. Even at low levels you can spam your q and then follow up with other abilities when they're slowed. Good guide overall though and i like the formatting. Maybe more pictures or bolded things to break it up though? Also you don't really explain match ups. Plus 1

Also, 2-second hard slow is much better and helps in hitting the rest of your skillset, hence proccing Organic Deconstruction.

Liandry's Torment is a very good item on Vel'Koz. It's better not to buy Rabadon's Deathcap, but instead max your magic penetration to shread people in teamfights. If you get Frost Queen's Claim, I wouldn't go for Twin Shadows to boot.

9/0/21 masteries are better for supports than 13/0/21 due to Executioner being of much less benefit than extra 10% CDR (on items as well) and free mini-mobility boots. Alternatively, you can go 21/0/9 but I wouldn't recommend that in most cases, as when you fall behind you have little means to catch up fast.

Regarding runes: there's no reason to pick gold/5 quints anymore. Stick with AP or armor. Also, you should run full flat HP seals for more durability, you're going to blow up against 1 combo from Leona otherwise. I do see the idea of more mana regen for better skill spam, but Vel'Koz already has low mana costs and build mana regen first via Spellthief's Edge, so it has less effect and leaves you too squishy.
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Glyphs, I'd recommend magic resistance for magic -based enemy teams, and AP for dominant matchups. Magic penetration marks are better for Vel'Koz than hybrid, that is correct.

The coding is solid and easy to look at.

well, in my opinion:

Ignite does not work well on Vel'Koz because its range makes you do a bad positioning in order to use it. Exhaust is a better option for escape and survivability that gives you better outcome.

Athene's Unholy Grail is picked when playing mid because it gives you magic resist, when playing support you need less magic resist and more debuffs, Morellonomicon gives you more AP, a decent mana regen that suits your needs along with Frost Queen's Claim and the same debuff Ignite does but from any range you got. Also Morello is 400Gs cheaper, and this gold you can use for Boots and a ward or a Ruby Crystal for your Sightstone

Mobility Boots has less mov speed in combat, what means that if someone hits you your speed is cut off, so you can't escape

Talisman of Ascension gives you more mana regen that you can possibly use, so its not cost-effective, for the active escape, Frost Queen's Claim gives you a similar escape.

you are a support poke, so why do you max Void Rift first? this way you will steal your adc's farm and you highest range poke will cause no damage. other thing is that Void Rift deals almost no damage on the first hit, and is the easiest thing to avoid the second one. you need it in your pocket to apply Organic Deconstruction twice during an engage, but you don't need to max it first.

In that case, why not get Spellthief's Edge? It gives decent amounts of mana regen, and any harass you do will give you gold. It also gives 5 AP, and later can be upgraded to give even more.

Why wouldn't you buy a gold income item or Doran's Shield at the start??

You really need some Coding. Take a peek at the guide in my signature for tips on how to code out a guide.