There is a trick that is very versatile, costs very little and has been done for at least 100 years. Newspaper. Take a full sheet, fold it on its natural crease and pull in up your jersey, waist to just over your shoulders. Tear a vertical tear down 6" at the neck and fold back.

When you warm up, sitting up and pulling it out is very easy.

Arm warmers are also very versatile. Easy to push down to your wrists going uphill then pull back to descend. Armwarmers and newspaper combined are very close warmth-wise to a light cycling jersey.

In any case, the trick is to ride wearing layers. No one heavy garment. Instead lots of light layers, none of which should be waterproof or fully wind proof unless it is raining or very cold respectively. Also plan your ride so that you have asy to take off and store first layers (or start dressed a little too cold) so as you warm up, you can keep from sweating. (I do not like the start cold approach. I'm skinny. I run the risk of never being able to warm up.) Warm hats are a good trick if you can make a quick stop to take it off.

There are lots of tricks. This is just a start.

Ben