What should you skill on Invoker?

I've been trying to get better with Invoker, so i was wondering what build should i go for?

NEVER follow 1 build.

It depends on the enemy lineup.

Need mana burn, disruption in teamfights and disables - WQ
Need control and fast push - EQ
Have enormous control in team, but lack damage - EW

Also NEVER skill them evenly.

quas wex and quas exort are the two legit builds. skilling evenly is really bad since none of your spells will be good. and wex exort is a build that you only go if you screw around in pubs.

quas wex is the more defensive, running around and making space for your team build.
quas exort is the more agressive farm oriented build.

quas exort is probably the best of the two builds since the EMP nerf.

The usefulness of both builds really depend on what you can play and what the enemy can't deal with. What you will see often when you pick Invoker is silences and lockdown and/or generally a more teamfight oriented draft.
In this case QW is the superior build since you can initiate from a longer range early- midgame and the mana burn from EMP severly reduces the usage of skills during an engagement. Also the movespeed from Wex is extremely useful for positioning.

If the opponent team lacks in lockdown and silences QE is superior because you can freely cast your huge dmg spells. Your rightclicks on QE will also hurt a lot with the bonus dmg from Exort. Your pushing power is also very high especially if you pick up a Necronomicon.

On 3k and up MMR you will probably want to focus on QE builds since BKBs will be everywhere making you pretty useless on a QW build.

Just depends on your comp/strat and the enemy comp, QW rekts some deathball comps, destroys some heroes that are either reliant on their mana pool like Enchantress, reliant on their positioning like Sand King or have low mana pools and is better in assisted ganks.

QE has a lot more damage, great in aggressive lineups, better pusher/sieger, helps an aggressive tri-lane be more successful and rekts a lot of heroes with low armor. However this build IMO is harder to play than QE, requires a more micro thanks to Forged Spirits, better positioning for more efficient Cold Snap/ Ice Wall usage and you won't have as much movespeed compared to QE.

It depends on the Early-Mid Game (before you hit 4-7-7-4):

4-0-4-1 gives you 2 Forge Spirits for Early Pushing/Split Pushing and Farming

3-4-1-1 gives you plenty of control and is better suited to Teamfights and Ganking

To put it simply, it depends on whether you should be mostly Farming and Split-Pushing or Temfighting and Ganking for the 1st 40 minutes.

Wex- Exort I've never really seen yet, so I can't comment on it. ._.

I love QW, it's my go-to option and I'd recommend it to you over the QE TO START.

QW you have less spells to worry about, and there is so much control... but not a lot of damage.

But yeah, as had been said, always vary your skill/item build.