Leg/knee warmers, arm warmers, and a cycling vest can extend your season quite a bit, without spending a ton of $. Even more, if you invest in a base layer for under your jersey. For anything under 50 degrees F, I go to my tights (both light and heavy duty thermal ones) that do not have chamois. On some cold days, I wear my Ibex (wool) tights that are my x country ski tights.
A lightweight fleece beanie for under your helmet, different long fingered gloves of varying thermal intensities, and wool socks/shoe covers make a huge difference. If your hands and feet are cold, nothing feels good.
2015 Trek Silque SSL
Specialized Oura
2011 Guru Praemio
Specialized Oura
2017 Specialized Ariel Sport