First off, all 3 builds (AD, AP, Hybrid) should have high Attack Speed (AS) and some amount of Cooldown Reduction (CDR). All builds use [W] for that % damage. Even in AD builds it will deal alot of damage to champs. Some form of CD will help.

Also, Kog has no escapes. You can build some Health but you're going to go down fast either way. Best option is lifesteal/spell vamp. Once you're dead remember to give a last hug goodbye to any near by enemies :) Getting your team to protect you is the best form of defence you can get.

As for which build is best, they are all good and viable really. AD Kog will probably have a tougher time early game but more dps late. AP and Hybrid combines long range spells and high sustained damage at safe distances.

[Passive] Icathian Surprise

Tricky to use, but after you die, you can move koggy for 4 seconds. After which, he blows up dealing true damage to near by enemies. Aim for carries, but try not to die :P

[Q] Caustic Spittle

close-range burst. Has good AP Scale (0.7) but short range. The armour burn isn't very useful to us, but the Attack Speed is. 30% at rank 5 for free is very good. and 10% at rank 1 helps farming.

[W] Bio-Arcane Barrage

causes our auto attacks to deal additional magic damage based on 2% -> 6$ of our targets max health. Capped at 100 vs monsters. Scales nicely (+1% per 100 AP) and with high AP and AS it will eat tanky and squishy champs alike. The additional range helps keep us away from the front line as well.

Keep in mind the CD is 17seconds. And the uptime is only 8. You will need CDR.

[E] Void Ooze

This is our main poke. Huge 1.0 AP scaling and 20% -> 52% slow as well. It has a decent width and will allow you to escape most chases. Use it to help teammates chase/escape as well as to make landing your ult easier.

[R] Living Artillery

Eats mana if not used correctly but has range so far you can target into the fog! The damage might not seem huge at first, but remember this:

It's cheap (40mana + 40 for each cast within 6sec) Don't go over 6 stacks. 3 for poking in lane.
It has almost no Cooldown (2/1.5/1sec)
It can be fired safely at ranges enemies cannot counter-attack from.

Use it to poke them down and fear pushing in lanes you are in. Great for defending towers with your [E]

Sorcerer's Shoes
Gives us extra Movement Speed and Magic pen. Something that is lacking in this build.


Nashor's Tooth
High attack speed and Cooldown Reduction, good AP, Mana Regen. Everything we need!


Seraph's Embrace
+1000mana for spamming our ult, Mana regen and AP. If that wasn't enough


Rabadon's Deathcap
Just flat out AP. And the +25% AP from other sources is very nice.


Runaan's Hurricane
This item is a great late game item because your [W] will be strong enough to use. bt get this, it will now affect TWO ADDITIONAL CHAMPIONS! So in a teamfight, you can hang back and melt faces.


Muramana
Be sure to get an additional ToG after the Seraph's Embrace so it can be charging. The AD is nice but the reason we want it is for the active. Consume mana to deal even more damage! and again +1000 mana = more Ults, more AP from Seraph's Embrace

nb
I have never been in a game long enough to try this last item out. But Hextech Gunblade, Void Staff or a Rod of Ages (built earlier) would probably be the best alternative.

Again, standard AP runes. We choose flat Mp5 over per level because we get Mp5 from items later on. We need the regen early.

You could swap AP Quints with Movement Speed if desired as it can help escaping and chasing. Especially chasing with your Living Artillery! But it will hurt your early game damage.

So the tactics with this build is to shell your enemies with your Living Artillery until they are weak then move in for the kill with your Void Ooze and Bio-Arcane Barrage. As they retreat, you use your Living Artillery to finish them off. Remember that, Runnan's Hurricane applies [W] to 2 additional targets at extended range. If you can safely Auto Attack [AA] with it you will destroy them.

The only defence you have is the slow from your Void Ooze. So try to save using it when extended in your lane. Once you're lv6 you can poke with it instead.

In teamfights you will poke them uncontested. You can then slowly push a lane or engage a teamfight [TF]

In teamfights you have 2 goals:

Staying alive
and
killing enemies

what you should do is spam your Living Artillery and save your Void Ooze for when your team engages or when they group up. This will help keep them from getting to close to you. When the teamfight start use your Living Artillery on the carries to take them down fast and safely from range.

Once 1 or 2 of them are down, move in for another Void Ooze followed up by Bio-Arcane Barrage and Caustic Spittle on your main target. You should be on full/high hp when you do this and they should be wounded. Your fast attack speed (2.0 ish) and 6-11% hp per hit (after MR) should eat them. Remember Runaan's Hurricane hits 2 additional champions. Which have prob already been damaged by your Void Ooze and Living Artillery.

Goals:

Stay Alive

Farm

Buy Tear of the Goddess

Optional Goals:

Poke enemy

Zone enemy

Kill enemy

This may seem simple but remember, you have no escapes. If you use your [E] to farm/poke you can only flash to avoid a gank. And even that has limited success rates. Untill you get your ult, play it safe and farm minions doing the occasional poke when suitable. Recall ASAP once you have 700g for the Tear of the Goddess. It takes a good 15min-25min to charge. If you can get blue it will help charging. But this guide is not reliant on blue.



Enemies may become aggressive and zone you. In which case hang back, [AA] minions as best you can then clean up with a [E]. If you can aim for the enemy as well. But a good opponent will know you are weak early game and will try to poke you while dodging your Void Ooze. If you miss your Void Ooze back off immediately! You have no form of CC left and the most significant part of your damage is on CD.

Don't use your Bio-Arcane Barrage since it will cause minions to attack you. And damage per mana spent, isn't very effective unless you can use it for the full duration. Which is still weak without AP or AS.

Caustic Spittle won't deal a lot of damage early on and has a short range. Your better saving the mana for another Void Ooze most the time.

You should have a decent poke with your Void Ooze now and hopefully nice mana regen [MP5]. Spam your Living Artillery every 6 seconds. This will charge your ToG and poke your enemy. When combined with your Void Ooze you can get a few shots off. But try to use it to clear minions AND hit the enemy.

Junglers will start to show a heavy presence now. Remember to save your Void Ooze when you are over-extended. Fire it and the jungler and run in the other direction. 9/10 you will get away. Keep spamming your Living Artillery and get the charges flowing.

Once the enemy is low fire your Void Ooze move in and then use your Caustic Spittle. These have strong burst damage now and typically cause them to retreat. Activate Bio-Arcane Barrage and then [AA] followed by Living Artillery. If you think you can get a kill use ignite. Just watch the mana as spamming Living Artillery without a 6sec break will eat mana very fast.

Teamfights should start breaking out near the end of this phase. getting blue will allow you to spam Living Artillery and force them to retreat all the back to nexus! Take advantage of this. They will do two things:

recall and heal
-or-
engage

If they engage you "should" have the hp advantage. If they recall push harder. When they regroup they may want to engage again. You will likely be the main target. Hang back as best you can while still doing damage.

This is pretty much the same as the teamfight section above since laning is over by now. Remember your Living Artillery gains range each level. between Rank 2 and 3 you can poke safely behind your tanks/brusiers.

Use it to check buffs/dragon/baron as well as brushes before entering them.

You will need to alter your items of you get focused in teamfights. Glass Cannon works because of your execeptional high damage and long range. Your team need to protect you so you can protect them. considering you only have 1 or 2 item slots you can change, your options are limited in defence.

A Hextech Gunblade will keep you healthy vs sustained dps

A Rod of Ages, Frozen Mallet or Banshee's Veil may help you survive burst

But as mentioned above, your escape options are limited and sometimes it's better accept your death, build full damage and take as many as you can down with you. Even if it's just 1 person, you can deal a nice chunck of damage with Icathian Surprise to the other team after death. It's a teamgame, and if you die so your other teammate can push, you did your job.

But if you are really struggling staying alive, just hang back and just your your Living Artillery to deal damage and Void Ooze to escape.