You know an epic game is coming. If you wanna understand and get more fun, you shoud watch these TV series and movie before playing Total War Three Kingdoms.

1- Romance of Three Kingdoms https://www.imdb.com/title/tt0108914
2- Three Kingdoms https://www.imdb.com/title/tt1514753
3- Red Cliff I https://www.imdb.com/title/tt0425637
3A- Red Cliff II https://www.imdb.com/title/tt1326972

Also

4- Three Kingdoms (2008) https://www.imdb.com/title/tt0882978
5- The Advisors Alliance https://www.imdb.com/title/tt7070302