Insulated layer
Not a wardrobe. One set to ride in, one set that stays dry.
What a plan says about it
The planner writes this from the ride you describe, so there is no version of it that is true for everybody. Here it is worked against one ride, named below, with a single answer changed at a time to show what moves.
2 nights · wild camping · cold but not freezing (8 °C) · gravel and tracks · towns daily
You stop moving at camp and it is 8 °C. This is the layer that makes the evening bearable rather than something to be endured inside the sleeping bag.
On that ride the planner marks it essential.
Ways to satisfy it
One object doing one job, so this is a choice between them rather than a shopping list. Every one carries what it costs you as well as what it gets you.
Down jacket
Warmest for the weight, and packs to almost nothing.
but Wet down is a wet towel, and it is the most expensive option.
A plain web search. We earn nothing from it.
Find one ↗Synthetic jacket
Still warm damp, dries fast, and survives being stuffed in a bag.
but Bulkier than down for the same warmth.
A plain web search. We earn nothing from it.
Find one ↗Fleece
Cheap, indestructible, and fine on its own in mild weather.
but Bulky, and the wind goes straight through it.
A plain web search. We earn nothing from it.
Find one ↗
Where to look
We hold measured dimensions for bags and for nothing else, so this hands the requirement to a search rather than picking something for you. Nothing on this page has a price, a weight or a maker attached to it, because none of those were measured.
A plain web search. We earn nothing from it.
Search for Insulated layer ↗Which one do I need?
That depends on the ride, and this page does not know it. The interview does, and it is the only thing here that can answer the question — no account, and every line it gives you names the answer that produced it.