MyPlace Guesthouse Hostel in Naha is situated perfectly in town. It's literally next to the Tomari port, which made the whole trip a lot easier. I've always enjoyed staying at hostels because of the social interactions and meeting people. However, this hostel is more of a place to sleep at, rather than a combination of social interaction. Luckily, I was with a group of friends.
Family Mart will be your best friend. Compared to Taiwan's Family Mart, it's an upgrade! I literally smothered myself with spam musubis and potato salad. I don't recommend to forgo everything for Family Mart. Do try izakaya and ramen places in town - get there by walking or taking a taxi.
I stayed in a 6 bed mixed dorm for $23/night with a shared bathroom within the dorm.
It has everything you need and a locker for security.
MyPlace Guesthouse Hostel
1F JEIS Building, 3-1-8, 3 Chome Tomari, Naha City, Okinawa-ken 900-0012, Japan