Get the book “Love your neighbor” by R Zelig Pliskin along with the Chofetz Chaim on loshon hora.
Then you introduce ideas from Choshen Mishpat, such as what you’d find in the Bavas, but even before you get to the gemara, you need to teach the concepts such as ribis, sechiras poalim, etc because chances are he is working and has to deal with business issues and needs to know these halochos now.