This ki thing really confuses me.

For example:
Istanbul´a tatile gitmiyorum.
Istanbul´a tatile gitmiyorum ki.

What´s the difference?

There is also one lyric that says: "Hayat ne ki sonuçta", but I still fail to understand it. I´ve read about ki, but it just doesn´t fit in.

Please Help!

In meaning there is no difference, the only difference is emphasizing [strengthening] the negative or interregotive statements.

Istanbul´a tatile gitmiyorum.  ---> I don´t go to İstanbul for holiday.

Istanbul´a tatile gitmiyorum ki. ---> I don´t  go to İstanbul for holiday.

Hayat  ne ki sonuçta ?  What is life all about ?

[At the end of the day what is life all about ?]

-------------------------------------------------------------------------

ki  as a strengthening particle

-ki  can be used to strengthen the question and negative statements.

-Beni istemiyormuş. Ne yapabilirim ki ? 

-He/She doesn´t want me. What can I do ?

-------------------------------------------

Davet etmezsen gelmez ki ! 

He/She would not come if you don´t invite him/her !

-------------------------------------------

Acaba rica etsen bu işi yapar mı ki ? 

Will [would] he/she do this job if you ask [politely] him/her ?