Kael

Pretty nice build, but after Aghanim's Scepter you better get a Scythe of Vyse, it's way more useful for your team.

I recommend moving drum into core after force staff. Its a great item on invoker and I wouldn't go right for the aghanims since it doesnt give you much in terms of usefulness (besides upgrading your ult but you can live without that for a few levels).

Stop spamming builds

Skilling Exort first. Ok, nice for lasthits / harass. But WHY skilling Invoke on lvl 2 ? Sun Strike with low Exort is useless