Ele/Me looking to expand

So ive made a Ele/Me and for the most part I have put all of my energy into fire magic.

We'll after reading throught these forums a bit I've seen Mesmers can be pretty useful if you know what to use and in what situations.

So my question is what are some good skills to start practicing with? and What are some key signs to know when to cast hex breakers and what not?

Thanks in advance