This is actually one of the easiest temperature zones for me to dress for!
Starting with my usual summer kit -- i.e, a short-sleeved jersey and bib shorts:
- as soon as it dips below 65°F I add knee warmers
- when it dips below 60° I add a sleeveless or short-sleeved base layer
- somewhere in that 55-60°F range I add arm warmers
- below 50°F I swap out the short-sleeved jersey for a long-sleeved jersey
- below 45° I swap out the knee warmers for leg warmers, and add a wind vest
- somewhere between ~38° and 32°F I swap out the vest for a jacket

Note, none of those temperatures are absolute, just general guidelines.