Make the most of the various European alliances within your family. Part of your marriage treaty included trading privileges. Focus on Scotland's economy. If you produce more local products for export, you can import luxurious items from the Continent.
Put the 'Black' Douglases in their place. You need more money to fund your queen's expensive tastes, and you wouldn't exactly miss their dominance within your kingdom. Attack them and usurp their lands.
Which card will you play?
Increase the taxes on all goods manufactured in Scotland. With the money from taxes, you can afford to import fashionable European luxuries for yourself and your queen.