There is a lot of discussion about what is useful and what is a waste of time. I think the merits of various approaches need to be grounded in the goal of the student.
If you want to read an occasional manga, memorize the common compounds and study some basic grammar.
If you're going to be staying in Japan for 6 months and then coming home, memorize some common sayings and basic conversational language.
If you're planning to move to Japan and write the definitive history of the Edo period, obviously you need to be academic and comprehensive in your study of the language.
Begin with the end in mind, as they say.
If you want to read an occasional manga, memorize the common compounds and study some basic grammar.
If you're going to be staying in Japan for 6 months and then coming home, memorize some common sayings and basic conversational language.
If you're planning to move to Japan and write the definitive history of the Edo period, obviously you need to be academic and comprehensive in your study of the language.
Begin with the end in mind, as they say.