Hi, im new to Invoker but i'd like to share how i prefer to build him.
As far as i can tell unless you do something completely and utterly wrong, like not start skilling invoke untill level 16, then there isn't really a right or wrong build, skillwise, for him.
This build focuses mainly on damage, and also increasing the duration the damage is on the field through skilling wex appropriately.
This guide is a work in progress as i play the hero alot will most likely change over the next few months.
As soon as you hit 5 be prepared to have Cold Snap (QQQ) already invoked and prepared to invoke Chaos Meteor (EEW) the meteor even with only 2 points in exort deals a substantial amount of damage combined with Cold Snap in the early game. Half of the time you will catch your opponent offguard if played correctly.