Types of Crops
Not all cultures grow wheat. Wheat is not a requirement for a low-tech culture. Starch, however, is. But there are many ways to get starch. From barley to arro root to rice to corn and on and on. I think the best way to figure out what your culture would be eating is to take a look at our own cultures. But, that's not always a perfect indicator, because there are some plants that just happened to evolve in a specific area and never had the chance to spread. If they'd had the opportunity, they might have become prolific, or they might not have. So, don't just focus on a single area. Focus on a given environment. If conditions are similar in two different areas, but those areas are on opposite sides of the Earth, they're usually going to have different types of plants. However, your area can have both.
That doesn't mean you should just toss in plants at random, of course. Crops may begin as wild growth, but the difference between "gathering" and "agriculture" is cultivation. Your culture chose to seed these plants, year after year. They chose to do the hard labor of making room for them and tending to them because these plants gave your culture something. Food or shelter or necessary raw materials. Agriculture isn't random. The most valuable crops are the most versatile crops or the ones that are most vital.
These are the ones that get the most space, the most time, the most attention. If you can make a lot of different things out of it, or you absolutely have to have it, you grow it in as much quantity as you can. For instance, when doing the worldbuilding for Born of this Soil, I was looking up similar environments. River delta, fertile soil, near the ocean, with a warm and moist climate. In researching I came across a list of crops grown in such an environment and saw 'persimmon.' It piqued my interest. I've never had a persimmon. I've heard of them, of course, but I really had no idea what they were.
So I did some research; you can make so much stuff from persimmons! Seriously: breads, coffee(ish), tea(ish), beer, molasses, pies, jellies, candies, wine, brandy. Pickle them, dry them, grind them into fine powder and sprinkle them on other stuff. And I thought—much as I'm sure many among my culture would have—well, that takes care of half my needs right there! And I liked the idea of the persimmon, versatile little weirdo that it is, being their favorite fruit. They're considered an acquired taste, and because the Andoli have been conquered and are living under the rule of another culture, I wanted them to have things that were very distinctly theirs. The ruling Ephendri think it's a horrible taste, but since they profit from the sale of it, they have no reason to want to stop persimmon growth or sale. My Andoli characters even make and drink bootleg persimmon brandy, wine, and beer. It's something they share with one another, something which does not get offered or given to the Ephendri characters—for the most part, although there is one (maybe two) with whom it's a point of symbolism.
So, choose your crops with the same care that your culture would. Really think about what their needs will be and how they can satisfy them. Crops have to be grown and harvested, and that takes time. Some crops can be harvested more often than others, some provide more bounty than others, and some take more care and attention than others. You don't have to know the entire evolutionary history of a crop in order to use it well—although, you know I won't stop you if you want to know!—but you should have an idea of when they can have it, how long they can store it, how much they can do with it, and how much of it they'll need. Oh, and who's harvesting it and when!
Plants and Description
However, even if you're making up your own fruits, vegetables and grains, or making use of something we don't to any large extent, you might also consider tying it to something familiar. If you don't want your culture or species to feel completely alien to the reader, having them enjoy something that is familiar can help. Of course, you have to be careful with this. On the one hand, there are words you can use to describe the taste that aren't references to our own world—such as sweet, bitter, sour, spicy, rich—and then there are words that relate to substances that may or may not exist in your background—salty, sugary, peppery, nutty, buttery.
It is possible that your world contains these things, but each world is different. Even if they're on your world, it's possible that your culture or species doesn't have or use them, or they're too expensive for most people. Knowing where these things come from, how and where they're most likely to be found, or how they are made allows you determine where they are and aren't.
This is another reason to consider a climate rather than a specific area. You can take plants from similar climates (the more similar the better, in fact) even if they do not belong to the same small geographical region. If you're worried that taking two different plants from radically different places will confuse the reader and make them unsure what they should be picturing, don't name the plant. Describe it instead. Can you name every tree you walk past? I can spot an oak, a magnolia, a dogwood, a crepe myrtle, a linden, a cypress, a birch, but I can't tell you want a maple looks like. I can't tell you the names of half the bushes I see just walking down the street. You don't have to name everything, name the ones that you think your readers will be able to picture and describe the rest.
Note: Yes, I know I said more on sentient plants next, but this needed less writing and I am slammed, so agriculture it is! Besides, maybe your wheat is secretly plotting to take over the world! :-D