You have to know that Japan's prices for western products are quite high. Western food such as cheese, butter but also clothing are all much more expensive than in the US and Europe.
Food
Food
Japan has it's own food. If you want to eat everyday some warm bread with marmalade and cheese you will spend your money in no time. Japanese food items such as rice, vegetables and fish are cheaper but still a bit expensive in my opinion. From time to time the supermarkets do planned discounts in a certain time range. But if you don't fully understand japanese this might be a bit though.
Throughout my stays I have notice that eating in small restaurants is much faster and cheaper. You can fill your belly for 500 to 1000 yen or $5-$10. For that, you get a big soup of Ramen or Katsudon or Gyudon or Tamago kake gohan and more. These meals come with a small clear onion soup and free water. In the same price range, is McDonalds, Kentucky Fried Chicken, Burger King and even Mos Burger (Japanese McDonalds).
Keep in mind as you walk through the streets that restaurants don't usually write the prices out like "200円" they usually use the kanji for hundred like this: 二百 (200) or even like this 五OO (500).
Clothing
Clothing can be a bit tricky. There a lot of department stores and places like Odakyu in Shinjuku. These places are expensive they have almost only brands. If you need clothing during your stay you should take a look at Uniqlo, Zara and other small stores that you can find outside of Shinjuku, Roppongi and Chuo. In Ikebukuro and other districts, that are further out they have more reasonable prices. Of course, you will find a lot of fashion but it's pricy.
Personal Care Products
You can buy you personal care products at Supermarkets, Konbini (convenience store) and Drug Stores. I would say Supermarkets are the most inexpensive of the three, Konbini helps you out of a pinch and Drug Stores are more expensive but they have a bigger variety. Drug stores have the Japanese word "Kusuri(くすり)" written outside which means medicine. Konbini are easy to recognise. The biggest ones are 7/11 (Big Seven written outside), Lawson and Family Mart. Both Lawson and Family Mart are written in roman letters so you will recognise them fairly easy.
Transport
Transport in Tokyo depends from the distance you travel. If you go 3-4 stations, then you pay about 160 yen. If you go some 5-6 stations, then you pay about 240yen. It all depends where you travel to as well. I payed 160 yen from Roppongi to Akihabara (11 stations) but 240yen from Roppongi to Shinjuku(4 stations). The easiest and most convenient way of traveling in Tokyo is with an IC card. You can buy either the Suica or Pasmo Card. They are both prepaid cards. All you do is touch with the card the IC card reader at the ticket gate when you get in and out. The card calculates your fare. You can use these cards to pay at vending machines and at some stores as well.
Suica requires an initial 2000yen charge of which 500yen are kept as a depositPasmo requires an initial 1500yen charge of which 500yen are kept as a deposti
※ Small Tip: The IC card reader can read the card through your wallet. All you have to do is touch the reader with your wallet.