A few more tips:
Download the phone app called Ramen Beast. When you are in Tokyo open it and enable location, and you can find select ramen restaurants based on your current location (or you can navigate around). Managed to fine a few, although some were closed today. But I lucked out on one that was really good and it hit the spot. Though you should school yourself about the style and do a little more research before you decide to try, since some places have no English and you should kind of know what you are going to order before going in. You don’t want to do the Bruce Lee thing and order 8 entrees of egg based dishes by pointing at everything on the menu.
Shibuya: walk along the streets around the crossing and there is a chitload of affordable eateries, so many to choose from and some look very lively. If you go to the nearby bookstores like Tsutaya or Tokyu department store book section there is Japanese magazine that reviews 100 bars/eateries places just within Shibuya alone and the variety is staggering. Maybe $70 or below per person with drinks, depending on what you spend and for the quality you get is a steal. Again research before you go, not every place has staff fluent in English. I encountered a new favorite place, though nobody speaks English in there and if you can’t read kanji or Japanese you won’t know how to order, but the local food and vibe is supreme and perhaps exceeds the satisfaction level of other fancy restaurants. So this is not a place I can recommend others, but my point is that there are lots of good affordable non high score non upscale neighborhood places that are amazing. Learn the language, if not some of the lingo and work your way in, then doors will open. I will also recommend trying to learn as much about sake as possible especially if you enjoy it, it literally will open more doors as you find common ground with locals who love it as much as you do (or if you end up loving it more than they do, they will be very impressed).
Have backup plans in case some reservations backfire or things don’t go your way for whatever reason. Look also for options your stomach can handle in the sad event that you fall ill.
If you want to experience food eye candy or even snack around, I recommend the food court basements of
Tokyu Food Show (basement of Tokyu Shibuya)
Hikarie B2/B3 level (Shibuya) though mostly for the sweet stuff
For fun, drop by Tsutaya Books 2nd floor Starbucks and marvel at the tourists hogging the windows seats sipping their lattes watching the Shibuya crossing, then chuckle and locate your next food destination.