Completely agree with godwine.
For souvenirs for your friends and family don't be afraid to check out the dollar stores i.e. 100 Yen stores. Japan loves it's 100 yen stores, heck there's even a TV show devoted to showing you what you can do/make with various purchases.
Green Peas is a big franchise to keep an eye out for.
As for souvenirs for yourself ... well I arrived with one suitcase and a backpack and left with two suitcases and a backpack
