Not a damn thing. I learned to do the opposite of what he did. If I followed anything he did it would be like following the blind. He's a co-dependant, stress freak, who is massively in debt and has a debt addiction. He listens to everyone he meets and considers them all "professionals" and will fall for anything. Actually I'm the one who tries to teach him. But it's hopeless. His moto is "It'll all will work out alright". Meaning he doesn't think anything through, just lets someone else tell him the path to take, and stresses out like a chicken with his head cut off until it's over. In the meantime someone else took a huge cut and got their money from him.
I guess if I had to try, it would be "look both ways before crossing the street". That's honestly the deepest thing he's taught me. That's pretty sad.