Invoker is a very versatile hero that can be played several different ways in several different roles with several different item builds. Noticing the popularity of the QE and QW build, the previously famous EW build had disappeared where the focus of players was to get Tornado + Meteor combo ASAP in the game.
Now, I have come up with a solid build for EW Invoker after a few test games in pubs and with bots. Through the tests, I have concluded that this build can work quite well depending on the player's reaction time and game sense (Map awareness, farm awareness etc).
This build is quite DPS-based with a touch of the standard Tornado > Meteor > Deafening Blast combo. This build serves to make Invoker a core hero with DPS and the ability to transition into the hard carry role.
Being a DPS-based build, Aghanim's Scepter is deemed unnecessary as the player only needs good decision-making to decide which spells should be equipped in his arsenal during a fight or when farming or when pushing. The build encourages the use of Alacrity + Cold Snap a lot.
The skill build is just a recommended version but in the end the skill build remains up to the player as I personally suggest maxing Exort for full damage output from your Meteor and Alacrity.
The skill priority in this build is Exort > Wex > Quas.
Invoke can be put at any levels you desire but I recommend only 1 level in Invoke until you can max it thus adding the skill at levels 15, 16 and 17.
Due to the high damage output of Alacrity + 3 Wex instances, there isn't a need for too many levels in Quas early on for Cold Snap. Sometimes even just one level in Quas may be enough but it all depends on who your opponent is.
As elaborated in the introduction, this guide focuses on the use of Alacrity in particular. Alacrity can be used to push, farm, fight. It is a skill that can be used to dish out huge amounts of damage and it can also push Invoker into the carry role when needed. That aside, you can also use Alacrity to boost the DPS output of your carries which commonly in pubs are Phantom Assassin, Faceless Void, Anti-Mage, Sniper, Ursa, Wraith King, Legion Commander and others. These heroes all benefit greatly from the +80 Damage and Attack Speed.
During your early game stage, I suggest using Chaos Meteor + Sunstrike. It is not a legit combo due to the obvious lack of disables but this is only for your early game where assuming you are playing mid, the Meteor serves as a huge ball of damage with the Sunstrike to finish if needed, also use Alacrity if possible and right-click the enemy hero as much as possible for maximum damage potential.
I suggest having Tornado + Meteor ready when you sense a teamfight about to breakout as you can deal a lot of damage with that combo, adding a Deafening Blast afterwards is of course good for full damage output and disarming the opponent's DPS heroes or hard carries in the fight unless they have BKB. After casting your full combo in the fight, casting Alacrity on yourself with the same item build as suggested will allow you to dish out a lot of DPS in turn during the teamfight.
You start off the early game with 2 Circlets, 2 Branches and 1 set of Tangoes. The Tangoes do not need to be explained whereas the Circlets are to upgrade later on into a Bracer and a Null Talisman and the Branches are simply for some early game stat-boosting.
It is recommended that you finish Drums, Treads and your Null Talisman by around the 12-15 minute mark. After finishing that, pick up an Orb of Venom to build into Skadi later as well as to act as a cheap slow against enemy heroes. Rush the Blink Dagger as soon as possible for positioning and escape purposes.
After getting Blink, start farming Maelstrom to increase your DPS as well as your farming speed. Get the Scythe (Hex) as fast as possible after Maelstrom for the mana regen and disable. If necessary, get Hex before Maelstrom.
By late game, supposedly around 45-60 minutes, you want to have a core of boots (Treads or BoT), Scythe of Vyse, Mjollnir, Skadi, Blink Dagger and either 1 DPS item or keep the Drums unless you can and need to get something better. Daedalus and MKB are often considered the late game damage items as they can help dish out more damage with either a crit or a mini-bash. MKB also gives True Strike which can be helpful against late game heroes who buy Butterfly. Butterfly is considered a DPS/Survivability item for Invoker because Butterfly provides immense attack speed further enhancing the DPS-output of Invoker and 30% Evasion giving you survivability against those who do not buy MKB.
For situational and luxury items, BKB is situational depending on what you're up against. Hex and silences specifically are annoying to Invoker despite being run on DPS. The point of this build is to stay back in a fight and dish out your Tornado > Meteor > Deafening Blast combo and sit there and right-click everyone with an Alacrity buff.
Force Staff is situational as it provides mobility and escape mechanism to Invoker. Unlike Blink Dagger, it does not get disabled though it costs mana, it is also okay to go for Force Staff if you prefer it over Blink Dagger. These two items are my favourite items in Dota 2 so I always welcome both.
Heart and Linkens are situational as items that make you tanky although Skadi already makes you quite tanky. Linkens' Spell Block is good against Flaming Lasso, Doom and other single-target disables which can delete you from the fight.
Heaven's Halberd is another situational item, something I added because as an Invoker, you often get a nice chunk of the farm and gold so you have the gold to buy it where your supports don't. Heaven's Halberd was specifically added due to the pub arrogance of the popular Voids and PAs who do not buy BKB. Disarming them with Heaven's Halberd will make the fight an easy one. Heaven's Halberd also provides Evasion and some tankiness for Invoker.
Refresher Orb isn't particularly recommended but it an be the tip of the scales in a teamfight with a double Meteor + Blast. It is recommended perhaps as a seventh-slot item in a >6-slotted Invoker.
Desolator is Luxury as it only provides damage and armor reduction which can work well with Forge Spirits but it does not give you attack speed. In late game, attack speed allows more DPS with more attacks compared to more damage in each attack with less attacks.
Divine Rapier is purely situational as you only buy it when you are desperate to win, do not buy it as a cocky stomping item.
*P.S. I know this is really long, but always always keep a TP Scroll until you get BoT.
As mentioned earlier, this build can work well to boost other hard carries.
This build is best put together with heroes with DPS-boosting auras like Drow Ranger, Vengeful Spirit, Luna and Beastmaster.
The focus on Alacrity makes this hero uniquely capable of boosting your hard carry with a Magnus or an Ogre or both because Alacrity + Empower + Bloodlust will allow an average maxed out hard carry dish out an average of 800 damage per second before reduction.
This build can work well with Legion Commander and Vengeful Spirit, especially in late game. Armor reduction from Vengeful Spirit and Forge Spirits increases damage output significantly. Alacrity + Press The Attack on Legion Commander during a duel may just help Legion Commander win the Duel in less than 2 seconds.
Thank you for reading this guide, I hope it helps and you will understand a new way of playing Invoker. Do not restrain yourself from giving feedback or suggestions on the guide whatsoever but do keep in mind that not every player may be on the same skill level and may be able to fully visualize how this build works. I may have succeeded with it several times now but it does not mean you will succeed too.
Good luck, have fun and Happy Dota ^^