It is also worth mentioning that there is a significant portion that could, in a crisis or if my circumstances changed, be reduced or removed from this spending plan without negatively impacting my health, but this is a comfortable way for me to shop for food without spending a great deal of time to do so.
I spend about 100 bucks on food for myself each month, and I'm finally gaining a little bit of weight.
I recommend getting in a good high fiber carbohydrate to use as your base for calories. I like to mix rice with beans, but potatoes are also a good base, and are quite economical. I actually recommend getting both potatoes and rice, since they are cheap and keep well. Oats are also nice.
Next up we should tackle vegetables. I don't know what you like, but you probably do. Buy those and cook them cheaply, by steaming or baking them until edible. I usually pick a price that I am willing to pay per pound or unit, and then only buy vegetables in amounts that I am definitely going to consume when under that unit price. In general, I get leafy vegetables and root vegetables of some kind every month.
Fruits are also subject to the unit price phenomenon. I like to buy under 1 dollar per pound for fruit, but for certain things I will go over that, like berries or dried fruit, either because I love them (dried fruit) or I can use them sparingly compared to other fruits (berries).
Meats are a great way to hit a number of nutritional goals and potentially gain weight, but there is a lot that you need to be concerned with when it comes to meat from both a procedural and a budgetary standpoint. Comfort with the supply chain that the meat takes from conception to the market, handling between your purchase and your storage, and processing in your home can be somewhat daunting, especially if you are not a confident cook or have some qualms with the current state of things. And on a purely budgetary basis, meats can be really expensive if you don't shop smart. I try to pay well under 5 dollars a pound per meat, and prefer to stay as close as possible to 1 dollar per pound. I like to buy chicken (bone in if possible, so that I can make soup), beef (also bone in if available, because marrow is delicious), and lamb (bone in if possible, which is almost all the time because I usually get lamb from an abattoir). If you watch for sales or have good relations with a slaughterhouse or butcher, meats are eventually available for around a dollar to three dollars per pound depending on the type of meat (chicken, beef, etc). That is when I stock up. Once I get meat home, I usually do one of a few things with it. I will either immediately put it into the refrigerator for use within the next 2-3 days (before the sell by date on the package), put it into the freezer for use within the next couple of months (food in the freezer is good for up to a year if processed correctly), or I will prepare it immediately for use that day. I like to poach or bake my meats, to ensure that they are thoroughly cooked.
Dairy is a great way to improve the variety of your meals, and add additional vitamins and minerals to your diet. I buy milk at its regular price, which is already pretty low considering that a gallon of milk is 3.7 liters and less than 4 dollars for me no matter where I shop. Cheese is pretty expensive, but if you use it sparingly it lasts for quite some time. I recommend being price conscious when buying any dairy other than milk though, because most other forms are ridiculously expensive.
I like to buy eggs, for several reasons. I enjoy using them to add additional protein and exciting textures to a dish, they are very quick and easy to cook (5 minutes or less, stovetop or microwave), and nutritionally they are quite valuable sources of essential B vitamins.
It is important to note, however, that fresh fruit, vegetables, and milk will usually not last a month in your home, so you might want to schedule several trips or buy more durable forms of those (dehydrated milk, dry fruit, frozen vegetables) to use after the fresh ones are consumed.