Knee/leg warmers are a good investment. I wear knee warmers when the temps are in mid to upper 50s and leg warmers, from mid 50s to upper 40s. When it's really cold out (in the 30s and below), I wear knee or leg warmers under tights.

Arm warmers (Terry boleros) are great too, but it's probably better to invest in long-sleeved base layers (wool is best). You can wear them under short-sleeve jerseys and wear them with other layers on colder days.