+1 on getting a JR Pass and a Pocket WIFI. Not all bullet trains, buses, local trains and ferries are accessible using a JR Pass though. If you are only staying in the Tokyo area,I think, there are three different passes to choose from. Not really sure on that, because when we went to Japan this year in early September, we opted for the national pass and it saved us $$ on the few times we used the bullet train to and from Tokyo, Nagoya, Kyoto and Anjo City.
The Tokyo train station is huge with tons of restaurants, shops and people (lots of people) to see, but there are only two camera shops in the station that are really small (maybe 40 x 15 feet) so your best bet would be to shop at the various camera stores elsewhere in Tokyo. Be sure to show your passport when you shop anywhere in Japan to get a tourist discounts (tax). Not all shops give discounts though.
A couple of things I noticed in Japan are, trash cans are few and far between and people riding escalators are always on the left side, unless one is in a hurry, they walk or run up/down on the right side. Just one of my observations over there.
You should look online to see if there are any festivals worth seeing in the time frame you will be in Tokyo.
Also, think about renting/buying an ultra wide starting at 8, 10 or 12 mm for those photos that 18mm won't be able to cover. And maybe something longer than your 50mm for those tighter shots during those festivals?