Need help with crit witch build

Hello everyone,

Istarted POE a few weeks ago and I totaly love the game.
I just went halfway through merciless with my crit witch but i'm starting now to have a really hard time making my build work.

I actually tried quite a lot of build combination but I still can't find a build that allow me to survive, do good room cleaning and can deal with bosses.
I can find some AOE that will kill most mobs but against stronger guys or boss I just can't kill them fast and I keep on dying.

As stated before I'm still quite a beginner and I would really need some advice on how to improve my build.

I'm running sort of a cold crit build but seriously I'm up to anything. Just give me advice on how I can tune up my build so it doesn't end up a total fail.

Here is a list of the items I currently have equiped and a link to the passives.

ITEMS

PASSIVES

ASCEND

Oh and I just want to add, that as I'm a beginner, I obviously don't have a lot of currency so the most budget way to fix my build would be welcome :)
Thanks in advance for any help you can give me !

Hi. It's quite similar to the build I'm making.
  I am currently completing Act 4 in Cruel and notice that I need to focus more on defense. I think having a gear with Evasion + ES and dedicating the following points to improving these stats could improve something.
  Tell me if you could improve it since I could use some advice.

  Here is the link to my build just in case: