DPI is the resolution setting of the sensor. A low setting moves the mouse slower, a high setting makes it move faster. Set it to what feels right for you. Some like it super high I prefer DPI to be around 2500 as the pointer moves at about the same rate as you move it across the surface. If you like making miniscule movements with the mouse that makes it jump from one side of the screen to the other, set it high. It is personal preference.
The poll rate of a mouse is largely a marketing gimmick. In normal use there is zero difference. Try them out to see what suits you.
Another thing I just noticed is it has the option for "Enhance Pointer Precision". This is mouse acceleration. What this does is move the mouse farther the faster you move it. It is almost always on by default. I have been using my mouse with it off for about a year now and has it made me a better gamer? Nope. Again, personal preference. Set it so it feels right for you, we can't really tell you how to set it.