Base layers are awesome this time of year. So much warmer. My base layers have lots of base miles. They come with sleeves – though I often hack them off. The have zippers too, handy when the rides extend into mid-day. There are scars from discarded pockets. Sponsor logos still doing their work long after the contractural commitment.
Old jerseys, make great base layers.
Depending on the day you can go with full jersey sans pockets or cut off the sleeves if it’ll be warming up. It’s amazing how warm a double jersey set up can be, and how easy to cool off by cracking the zippers.