After finishing the level 20 main quest, you can have access to the Technology system.
It may take you some time and resources to invest and research a technology, but technologies can help you a lot in every aspect of Siegelord. For example, the technology “Increase Production” enables you to obtain doubled resources from solving internal affairs; “Feudal Standing 1” enables you to recruit one more general. Therefore, when you have new technology available for research, don’t hesitate to spend the resources necessary to unlock it. If however it is a useless technology at the moment (for example it unlocks a higher gem level than you can currently build), you may wish to let resources trickle into development instead of draining a lot quickly. If you choose to do this you will need the technology later and it may go off-screen before researched, therefore to make forgetting until you need the skill less likely, note the skill and investments (like on a physical notepad or in a file you make to keep information on your Siegelord character).
Click on the technology icon in the bottom to open the technology interface. Here you can check the technologies you have obtained and those you have not. When there’s a technology ready for investment, you can research it in this interface.