I've been running without a watch so far, just with an app on my phone. About 15 years ago I tried to get into running and used a Polar with HRM, which I really loved. And I got myself a cheap watch with HRM a couple of years ago to help me lose weight. My GP (also a sports doctor) ascertained the pulse range I should exercise in (actually he scared me witless, as the range was so low even walking at my usual pace was difficult. He gave me the impression I was going to drop dead pretty soon. However 6 months of walking did the trick). But now this running business is getting quite serious and I think I need a serious running watch. So I've just ordered a Garmin Forerunner 235.
And I need new running shoes next month. Expensive business this running.