I can be of some help if you want to know more about the history of the Three Kingdoms. You may want to look into some of the Strategy RPGs that Koei released about the Three Kingdoms as some sort of basis of how you want to base your story upon. Potential main protagonists can include Cao Cao, Liu Bei, Zhuge Liang, Jiang Wei, Sima Shi, the Sun family respectively, but mainly Sun Quan, Lu Bu, and many more. It really depends on your preferences.