I found an easy to read watch invaluable for my nav exercises in my PPL. For me, the digital watches are quick to glance at and its handy if you want to set a couple of alarms for the odd mid-flight task.
I went for this:
Casio Men's Digital Twin Sensor Compass Watch
Big numbers, super easy to read if you're bouncing about a bit and under a little pressure doing a diversion exercise or something, and has an excellent backlight. Its got a reasonably good built in compass and thermometer too, pretty useless but it appealed to the nerd in me!