When it drops below 60 degrees, for the bottom, I would typically wear my normal golf slacks or some Uniqlo dress slacks. But when it goes below 50, I would typically wear corduroy pants as they tend to feel warmer to me. If it goes below 40 (yes, I have a golf buddy who's crazy, we played in 18 degree weather with wind chill. Hitting a wedge shot onto the green, and it bounces like it's on a billiard table )
For the top, if it goes below 60 degrees, I would likely use the running arm sleeves with regular golf polos. I would also put on a synthetic or down vest, so I can regulate the temp. If it goes below 50 degrees, I would typically wear a the synthetic/down vest on top of a thermal compression layer (UA, Nike, anyone's would basically do). These typically have fuzzy inner layers that makes you feel a lot warmer. If it's below 40 I would probably add another layer. And if it's below freezing, I wear all of those plus my Patagonia micro-puff with hoody. Oh and on those <40 days, a knit hat really helps.
As others have said, it's very important to wear layers as you can adjust easily to accommodate for temperature changes throughout the round. I find it very helpful to have a underlayer for heat retention (Uniqlo also have good heat tech undergarments).