Going TS Omni build, NEED HELP with tree and/or gears to upgrade

Hi id like to make a TS Omni and trying to follow this build
https://pobb.in/zeOTJ8X4zfMf

My current setup is this
https://pobb.in/ULJSkWxKdtUA

current omni is around 1800+

What gear should i upgrade first?
I also have other TWWT (phasing, + str & int, onslaught, hex), gems, gears but im not sure which of which should i pair with.

It seems my current build is having a problem clearing T16 map, mostly with those ghost like that suddenly explode and this is the reason why i am getting discourage to play.

another thing is i dont seem to have a mana regen per hit

I would very much appreciate if you can help me fix my build so i can go back to farming.