Some that I ride with wear shorts with short sleeve jersey in the low 40's, while others wear tights, long sleeve jersey+ and gloves at the same temps. It's just personal preference.
I prefer knickers down to about 40-50, then tights below that. If the temps start in the low 40's and get up to mid 60's, then leg warmers since they can be pealed off later.
My cold weather gear doesn't get used that often ----> FL