Build more farmhouses and upgrade them to the highest level. Be careful not to build too many though. You can click on individual buildings when using the “i” tab next to the chat tab at the bottom left of the screen, this will show you the current production rate and figures for each farmhouse. Most players tend not to build farmhouses that are below 4% production.
Build more decorative_items, PO. Once you have built all the other buildings you need, fill the rest of the castle with the highest level decorative_items you can. Decorative_items increase PO which in turn increases production of all resources.
It’s a careful balance between the resource buildings and PO. Check some level 70 castles and outposts and see what they have built. Usually, this gives you an idea as to how many of each you should build.
Overseers. Hiring the overseers significantly increases production of whatever resource you need more of. You can hire the overseers from the Kings_market. The standard overseers are located in the heroes tab. These overseers increase production of the selected resource by 25%. There are also veteran_overseers, these can only be hired when they are activated, which happens every few weeks. The Kings_market tab at the bottom right of the screen will sparkle when they are available. These overseers increase production even further and are added to the standard overseer percentages.