Garmin Edge 500. You'll love it. It does not have a "MAP" like Edge 800, BUT...you can go on MapMyRide.com, map it out, export the route, and put it in Edge 500 (also for FR 305), and then it will show up as a crude map, and you follow it like breadcrumbs.

Like this picture.

As you improve, you can add on more features, such as HRM, cadence/speed sensor (more reliable especially in woodsy areas). If you decide to get a bike, you can get Madone with DuoTrap built in the frame. Garmin Edge 500 is ANT+ capable, FR 305 is not.

Good luck! :-)

I have FR 305 because I also run, fwiw.