It's really hard to say how much to take. It depends on how expensive your tastes are. You can eat expensive meals and stay in 4 star hotels or you can eat ramen (the good kind not instant) and stay in more sensible hotels.
Also look at the guides by Hosetek on these forums. This is a good one to start out with.
http://www.japanforum.com/forum/japa...light=housetek
Reptiles have silly grins
Dark eyes--shiny teeth--some have fins
Samurai they smile never
Serious--pretty swords--very clever