If you're learning Japanese in school, or even if you're learning it on your own, I recommend the Genki I and Genki II books, and the corresponding workbooks. If you really enjoy it and want to come to Japan to use your newly acquired language skills, I'm confident that after getting through those 2 books you'll have enough Japanese to get by and you can have fun wandering around, reading signs, chatting with strangers, etc. Don't be discouraged by people saying that Japanese is so difficult to learn.
Edit: also, I hope this comment didn't come off as too negative. I think it's great that Duolingo is doing this, and if it gets more people to enjoy learning Japanese then that's fantastic.