I wear a base layer of some sort on virtually every ride
For hot weather (say 70 degrees to over one hundred), I'll wear this polyester hot weather base layer from Pearl Izumi
https://www.pearlizumi.com/US/en/sho...yer/p/11122105

For colder weather, I'll wear a merino base layer from Pearl Izumi
https://www.pearlizumi.com/US/en/sho...yer/p/11121923

I find the transfer mesh fabric of the hot weather base layer helps me regulate temp better than just the jersey alone, even when it's really hot. Seemed counter intuitive to me at first, but the fabric seems to spread out my sweat over a larger area so I cool better

The merino wool base layer is comfy, soft, and keeps me warm and wicks the moisture well so it doesn't get all loaded down and wet