The Trading Post is more than just a last resort. It can be a primary engine for your economy. Identify high-value goods that your settlement can produce efficiently and focus on selling those for Amber. Conversely, identify critical resources you lack and be prepared to buy them, even if it means a temporary Amber deficit.
Look for Cornerstones and Perks that boost trade prices or reduce trading post costs. Consider building multiple Trading Posts in larger settlements to increase the frequency of caravans and the volume of goods you can trade. Amber can be used to buy crucial blueprints, saving you from relying on random rolls.