New Gaming Mouse

Depends on what you are using it for and what you are comfortable with. Some people never go past around 800 DPI because they don't like the way it feels to them. It varies from person to person, so there isn't any real answer to your question.
 
Dpi is not what makes a mouse good or not, just try it out if you can and get it if you are comfortable with it.

It only determines the speed of your cursor traveling across your desktop, nothing else.