Do a search of the forums...there's lots of good advice about clothing

That said, in the 50s and 60s, I reach for arm warmers, knee warmers, and a lightweight vest. If I know that it's not getting above high 50s, I might wear knickers instead of shorts and knee warmers, and a summerweight long-sleeve jersey. My hands get cold really easily, so I'll often wear a pair of Manzella silkweight windstopper gloves over my cycling gloves once it's below 60.

All of these pieces are really lightweight and smushable, so they fit well in jersey pockets if I get too warm. It all really depends on how cold it is when I start, how much it's going to warm up, and how hard I'm working.

Data weenie that I am, I actually started keeping a spreadsheet of what I wore for a particular temperature. By next spring, I should have a good picture of what clothing works at what temp.