I've been riding with a Gore Phantom 2.0 jacket and one or two layers under it, depending on the temperature. For colder days (25 to 32F), a mid-weight Merino wool with a light long sleeve synthetic. For above freezing, either the mid-weight Merino or a light-weight Merino alone under it.

I've found that you really don't need too many layers under this Gore jacket--at least down to the 25ish (F) temp range.