As a retired eye guy, I can tell you the best spent money is a set of Wayfarers with polarized lenses. No, not cheap, but durable combined with good optics is a great choice. Brown polarized for a grey/overcast climate, grey for sunny climates. I have a pair that is ten years old and actually polished the white oxidation off the frame and put in new lenses. If you want or need side protection, then sport specific glasses may be better.

Another good choice is Marchon Autoflex frames. Light, durable, long lasting.

The only downside with polarized lenses is that it can wipe off the image coming from LCD displays. I had this happen today to me at an electronic kiosk. Push button? Where? Oh.....

Photochromic lenses are never fully the answer for a true sunglass, and some are still temperature affected. Most are based on polycarbonate lenses which are impact resistant but have poorer optics.