Invoker Exort/Q or W/Q(better after 6.79)

Getting started

1) Introduction
2) Item choice description
3) When to pick
4) When not to pick
5) Matchups - how to win/get advantage
6) Pro/Cons
7) Conclusion

Introduction

Carl, the Invoker

Invoker is one of the strongest mid heroes and is one of the most annoying to lane against because of forge spirits and coldsnap.
With 100+ Games and 10+ CM's(captain mode) i assume the risk to say i mastered invoker after long hours of training.

Items

Item choice

Starting items and laning phase is crucial for Invoker, as a underfarmed and underleveled Invoker tends to be useless.
I saw a big amount of people taking fast blades of attack with 1 tango which is kinda bad, unless u go quas/wex invoker.
Rushing for midas is not the best choice in most situations because Invoker has sh*t MS(280). Go for fast phase boots null talisman, and then rush for Midas. I consider Midas to be core on an exort/quas invoker, because he needs fast levels to be effective, while u can skip the midas if u're doing the Wex Build.
Eul's scepter is a situational item as it offers good MS, chance to avoid damage/stuns/disables or catch someone who's out of tornado's range(or cooldown). U can also do some nice combos - sunstrike, meteor, blast (1 target, but usually tornado, meteor, blast is better), sunstrike+icewall+coldsnap and others.
Agha is core for a good Invoker, as it offers the chance to use ur spells at their best, and opens the room to a good Pro Cast, especially combined with a Refresher Orb.
Desolator - good dps, scales well with forge spirits armor reduction.
Force staff - escape/intiating.

When to...

When to pick

U can pick Invoker almost in every game. Invoker gives a good mid-game potential for all ur team, while the main carry is farming u can in 4 own and dominate the rest of the team due to Invoker's AOE nukes and disables.
Generally u pick Invoker when u want to crush mid-game with several allies that offer u the chance (Dark Seer with his vacuum for instance).

Better not... or?

Avoid Picking

As the chapter title says, avoid picking invoker against good Lockdown line-ups (bane, doom, clock and so on) against silences and disables.
Never pick Invoker against an OD if u're going Wex/Quas. U'll have literally 20 damage, and 0 farm. Exort/Quas is average against OD, but most of the cases a good OD ***** on ur laning phase.
Tinker is a good counter to Invoker because of his nukes.
Avoid picking invoker against fast pushing opponents. U'll be kinda useless. Fast push line-up = U have to group up with ur team in most of the situations. This means u'll be underleveled.

BEWARE!

Matchups

Winning with Invoker the lane is not a big concern if u're mastered him.
Cold snap forces enemy to retreat. So do the forge spirits. Sunstrike gives global radius to get easy kills on low hp targets.
I see Shadow Fiend picked many times against Invoker. I literally piss 1 on 1 against SF if he doesn't get help. Forge Spirits + Cold Snap + SS is generally enough to solo kill anyone.
Use forge spirits to harass and most important - to denie runes against heroes like SF, pudge, puck.
Never underestimate the forge spirits power. Send those 2 against a solo suports. If they don't run from 'em u have to land a sunstrike - TADDA, free kill.
Ok, now i'll try to explain the thing that i call a full pro cast on Invoker. Items required : Scepter, Refresher. Take in mind u have to be arround level 22-25 to do this effectively.
1 cast forge spirits. (900 range is underestimated + armor reduction, but well lategame not that good.). Have casted 2 spells, Tornado, Meteor. Force enemies to pop BKB with a simple tornado + icewall. Generally the BKB carriers will be affraid of ur procast and will pop BKB immediatly. If none has BKB, or it's a 4 sec and was used - take full advantage. Once they're grouped up, cast a long range Tornado (at least 3 have to be caughter, or u'll waste ur spells). As soon as u did it, cast immediately EMP and approach the enemy. Use EMP ASAP. U have ~1.4-1.6 to land the tornado + Blast combo. Refresh, blast and EMP. ~2.5 k damage, 800 is pure, and 50% of burned mana is restored for Invoker. HUGE nukes. Follow up with an icewall, coldsnap, tornado+meteor again regardless of the situation.
Generally speaking, people that realize the power with invoker will try to shut him down earlier. If u're a good invoker u'll be ganked very very often. Sometimes the gank can turn into a bad one if u are good enough. Always have the forge spirits with u. Just put them to attack suports that gank u. For example Chen comes with 3 creeps. Immediately attack with forge spirits chen. Cast cold snap if possibly. You can easily make a kill in a situation u were supposed to die if u follow with a good sunstrike.
Now about Wex/Quas invoker. Usually You go Wex oriented Invoker when u want to do the thing which i call "Crowd Control". The Wex invoker is harder to master because it's way more harder to lane. U have low damage, ur last hitting potential is not that good. Early game spam cold snap, rush for Eul's. When wex level reaches Arround 5 start using Tornado + EMP. That's the thing called Crowd Control. The amount of mana burned is HP removal in terms of damage. Follow up with cold snap if Possible. The Wex build doesn't have the RAW damage that the exort one gives, but it's more safe and in most of cases is choosed for CaptainsMode. A good item i like on a Wex oriented invoker is The Necronomicon. Those 2 combinated with ColdSnap gives huge kill ability. Also Necro3 helps to push, and scares enemies. (PURE DMG, last will).

More indeep

PROS : Good nuking potential, escapes, impossible to catch if Wex + Eul without good disables. ~500 MS with phaseb. Good laning phase. Global sunstrike for kills. Insane disables+disarm from blast.
Cons : **** MS early. Very VERY farm and level dependent. Easy to kill with disables. Useless against BKB kinda.

Chapter Title

Conclusion : If u're a newbie, don't pick Invoker on pub. Go on lobby and train hard. The key to a good Invoker is to be calm and very decided in what u do. The problem i had when i started i was panicking and hitting sometimes the wrong buttons, which was messing everything. U have to reallybe calm. The biggest mistake made by players - learning 2 3 basic skills. Invoker is a complex hero and you have to know when to use some spells and when not. Learn all the skills and their effect. Never be afraid to use everything. Ice wall for slowing enemies, or enemy creeps during the defense. The Fact that forge spirits have ~900 attack range, u can place the alacrity buff on 1 of them and safely attack the tower with creeps if u feel danger going highground (pushing T3). And so on. Use Invoker at his best.