My biggest learning point has been to look at the temperature rather than go on how I feel before I leave the house. above x: no jacket, below y: this jacket, below z, knee warmers + gillet. Takes the guesswork out of it.
If the house is cold and you’ve been inactive before you leave, you might feel like piling on more clothing. If the house is warm and it’s cold outside, you might be tempted to throw another layer on after you poke your nose outside.
A well-fitting synth insulated gillet is the best think for cold starts though, done up to the neck and you’re toasty toasty. If your core’s warm it doesn’t matter so much if your arms aren’t protected, especially for 3 miles. You get a bit of venting with the zip just a couple of inches down, and it’s barely doing anything if it’s less than half way zipped.