I used to order out all the time, and never cook. Recently I've given those food subscriptions a shot and have been pleasantly pleased. I went from not cooking ever, and spending an amount I am ashamed to post, to cooking a few times a week and reheating leftovers. Today I had the urge to make lemon bars. LEMON. BARS. Unreal.
Water is a necessity just to live, so getting a Brita filter is an inexpensive investment. Since I've saved so much from cooking at home, I have a water subscription of Icelandic Glacial via Amazon. I take a bottle with me to drink as I have a habit of losing those refillable bottles.
Fairway is one of the more inexpensive grocery stores in Manhattan, as is Associated which is available in Brooklyn too.
If you are interested in the cooking subscriptions, I have a few discounts I can send your way.
Hope this helps!