A lot of places in Okinawa take VISA and other cards/contactless payment, so keep that in mind, because it means you don't have to bring as much cash if you're a card user. If I were going there for a week I'd probably bring $200 USD to exchange for local currency. How long is your trip?

$735

If you're not going to buy anything then not a lot. If you are going to, then save a lot, buy rare items, and sell them for a lot more when you go back.

Twelvety million hundred!

Always keep in mind whatever you do buy and plan to take with you home the extra weight will cost a little fortune for your flight back home!

Hm, without knowing what anything in Okinawa costs, I'd say to look at travel expenses, the cost of where you're staying, and how much you want to give yourself per day for things like food, admission/tickets, souvenirs, that type of thing - maybe google restaurants and attractions to see how much they are?