You don’t say where you live. If you are from a warm climate (say Florida) you will likely feel cold when someone like me would feel warm.
I would never wear a down vest or jacket in April in Spain. Besides the fact that it would be too warm for me personally, once it gets wet it loses insulation. Better to have a light Primaloft or similar synthetic insulated jacket.
I would suggest a long sleeve light merino wool shirt that you can layer with a T-shirt or preferred hiking shirt. Use the insulating jacket if you are prone to being cold even when exerting yourself and carrying a pack. Don’t forget a light waterproof rain jacket.
I have a packing list that I used on The Primitivo in May. Just as an idea. But remember that I don’t find walking in 40 F degrees cold. Even in rain. But others freeze in these conditions.
http://www.musingsfromthelastfrontier.com/post-camino-de-santiago-packing-list/