Sometimes you can win a fight by not fighting, as fighting is actually really expensive and risky
Maybe consider feeding your army. That can be important both in times of war and peace.
Please do not lead a frontal charge uphill into a fortified enemy position. I can't believe I have to explain this to you fucking newbs, but it keeps happening so here we are.
Have you tried being sneaky?
Read history. Sometimes someone has done a thing before you and you can just copy their homework. Sometimes you can see someone else copying homework and use that to your advantage. Sometimes its just good to know about things other than what you, personally, have seen and done.
It's really good though but you have to be able to take the specific cases Sun Tzu is talking about and apply them to conflict more generally. Like the "look for different kinds of dust clouds to figure out what your enemy is doing" bit doesn't apply much today, but you can look for tell tale signals that offer insight on the actions of your enemies. Are the pigs on foot or in cars? What kinds of weapons are they carrying? Are they in regular uniforms or riot gear. It sounds obvious, but most people have the same understanding of conflict as those ancient noble failsons
Y'all massively overestimate how much the average person understands about conflict and struggle. Sun Tzu has an important place and doesn't deserve all this scoffing.
The Prince is basically the same. It's basically just "please just fuck with other nobles, and when you lock them up and steal their shit go and give it to the public or something, and don't fuck with the common people" and "it's ok that you're a huge dumbass, just please hire someone who's not and then let them do all the real work while you go camping and play soldier in the woods, also pack a lunch."
The main reason econ and poli sci majors are so obsessed with Sun Tzu and especially Macchiavelli is that the actual good sources on realpolitik are Mao and Lenin and that's considered too dangerous for them, so they get the safe stuff, the utterly nihilistic and immoral Borghia bootlicker and the "archers are kinda good for killing at a distance" drivel instead of having State and Revolution on their reading list.
The whole "appear strong when you are weak, and weak when you are strong" nonsense is so easy to spot when people and companies apply it. Everyone can tell when someone is fronting and faking confidence, or faking being humble, nobody is fooled.
Other stuff from The Art of War is more useful though.
Many modern translations of the Art of War are misappropriated and forcefully applied to business or politics.
Sun Tzu was a Taoist, who believed in simplicity, spontaneity, equilibrium, and so forth. He believed in flowing effortlessly like water finding is level and weathering a stronger enemy.
His writing exemplified a philosophy and a spirit of living as he applied them to war.