I reckon TextFugu’s enough for N5, but you’re going to need to practice listening a lot on your own. Maybe N4. I’ve decided to try for N3, personally, but after buying a study guide, I’m starting to think I may have rather overestimated my ability. Oh well…
Anyway, I’ve been studying with an iOS flash card app called Sticky Study, which is quite handy, but you can also buy mounds and mounds of study books. If you’ve got a local Kinokuniya, it’s certainly worth trying there, but even if you don’t, maybe you can order them off the website. http://www.kinokuniya.com