Each couplet strengthens the argument with another image. The progression moves from the foundations of friendship to measures, cultivation, trade, debts, the grave, and clothing.
The images do real argumentative work. To measure affection fairly is to think about giving and receiving; the fruit of cultivation makes conduct resemble a harvest.
Read each verse at two levels: first identify the literal object, then the human relationship represented by it. This makes the difficult vocabulary an active part of the story rather than a separate list to memorize.