For gaming, 800, 1200... More than that wont matter really. For high resolution desktop, maybe something higher might make sense. I'm 800, eDPI 3,200, that's about.... 45 cm mouse movement / 360 degree? That's usually how you measure mouse sensitivity in-game, for like FPS and 3rd person. Actual mouse DPI is mostly irrelevant.
EDIT : EDPI is useful to compare relative mouse sensitivity in the SAME game. Because games have different idea of what their sensitivity slider means, cm/360 or inch/360 is more useful in absolute terms, comparing dpi between DIFFERENT games.
Also, when measuring absolute sensitivity on your desk, make sure you have no acceleration, even if you use mouse accel in games. Otherwise, the measurement will be skewed. Mice nowadays are accurate enough, or should be accurate enough that a doing 360 turn at any reasonable speed would measure the same on the pad.
If you want to see what the pros are using, there are plenty of charts around. It's fun to see, but usually, in Overwatch anyway, it's between 2500, to 5000 EDPI, or roughly 30cm to 60 cm on a pad for a 360 turn. Low sens players sometimes use button (like a sniper button, but reversed) to increase the sensitivity momentarily, for doing 360s or whatever. Some pros actually use extreme sensitivity (low or high), but they are few and far between.