XI is broken in a way that once you take over someone with good officers, it becomes easy mode from then on. Eliminating anyone that has the potential to grow early on like Cao Cao or Sun Jian in the early scenarios is a good way to be safe. Once they're eliminated just send everyone to jail and from there you can hire them all.
Blocking those mountain roads and plank roads with a camp to hold off enemies is a viable strategy as well. Other than that, grab Juggernaut asap, build Archer Towers, make sure you always leave 20,000+ troops behind to defend. The AI is always quick to attack you from the back when you're launching an invasion on someone else.
Beta: Zhen Langcun
(23) 70-90-54-36-50 Blitz, Duelist (e), Charge, Raid, WeaponmasterTheme
v6 (?):Zhen Xian (21) 76-81-60-41-60 Charge, Duelist (e), Investigator, Raid, Weaponmaster
Jia Yunli (24) 38-41-68-81-81 Artisan, Administration (e), Charming, Networking, Propaganda
Xun Lique (30) 67-36-81-60-70 Arrowstorm, Spy, Tactician, Wile (e), VolleyVersion 5: Hao Xian zi HuXin (Lawful Good)