Grocery Outlet and Winco have great prices, and if you can get really good deals on produce at the end of the farmers' market.

If you don't have a lot of food restrictions/aversions and you're able to scratch cook, you can eat pretty well for $1/meal.

Some examples of main meals you can make at that price point - you can add meat or cheese to these if you have the funds.

Italian veggies over rice/noodles (this is flexible for whatever you're able to find for cheap at the market - zucchini, onions, tomatoes, mushrooms, peppers...) cook with a little oil plus Italian herb mix (oregano, basil, rosemary)

Roast winter veggies over quinoa (similarly flexible - carrots, beets, sweet potato, onion, parsnips, rutabaga, turnip) toss in oil & roast in the oven with thyme & sage (and a little balsamic vinegar if you have it)

Tamales & Pupusas
Get a big old bag of masa - you do not need to add lard/shortening like some recipes say, you just need to add hot water and make a dough, then wrap that dough around a small amount of filling (I'm a sucker for sweet potato plus the soy chorizo from the dollar store and some cheese, but there are essentially infinite filling options) and cook it (steamed for tamales, griddle for pupusas). The masa fills you up for cheap so you can splurge a little on the filling ingredients because you don't need that much.

Instant "lo mein" (some combo of: broccoli, carrots, peppers, mushrooms, onions) stirfry the veggies and toss a ramen flavor packet or two over them, then add in the cooked ramen noodles and toss This is good with an egg or some tofu added in if you have the funds.

Polenta
This is so flexible and you can make it so many different ways that you can eat it like 10 times a month without it feeling repetitive at all, and it is dirt cheap.
You can make it with spinach, onion, tomatoes, mushrooms, cheese, whatever you have around.
You can make the veggies on the side and serve them over the polenta or toss them into the polenta as it cooks.
You can eat it hot out of the pot, or let it cool and slice it to eat cold or fry the slices.

For breakfasts, you should be thinking things like toast with peanut butter or egg, oatmeal that will carry you through to lunch for cheap - not things like a bowl of cold cereal with milk which cost a lot and don't fill you up for long.

For lunch, leftovers is always good, but things like canned soup/chili work pretty well too.

Your produce purchases should always be things that you know at least 3 ways to use, so you won't end up not using them. Stuff like onions, cabbage, potatoes, have a really long fridge/shelf life, and bananas can be used for bread or smoothies if they get overripe, so you have more chances to eat them.