What is your playstyle (how you aim) ? If you like to spray, I would use 1600-1800 DPI, 1000 Hz and small Gamesence. If you like to oneklick, it should be better to use 400 DPI, maybe 500Hz and 2.5 Gamesence or lower. It also depends on the mouse (laser), if you are using an older sensor you should try to find a good review on your mouse on overclock. Some sensors are less consistent on high DPI than others.
Also make sure that your Monitor is 1ms reaction time. If not use 500 Hz!
Only some tips based of my expirience in 10 years Gaming. Maybe other have a diffrent opinion.