It’s not practical to grow wheat or rice in your backyard garden. Both those grains need to be hulled in order to be edible. The additional time and expense is probably not worthwhile, for a small amount of grain. But certain varieties of barley and oats are “hulless”, and therefore easier to grown on a small scale.
The word “hulless” is in quotes because barley and oats have hulls. But for the hulless varieties the hulls fall away easily during threshing (separation of grain from the plant). So you don’t need a hulling machine. This makes hulless barley and hulless oats more suitable for prepping and survival.
Oats are a very nutritious grain, with a high protein content (16 to 17% protein by weight) and plenty of fiber. Oats can be eaten as a cooked breakfast cereal. Whole oats can be baked into breads and muffins, or the oats can be ground into flour.
Both oats and barley are good sources of electrolytes: calcium, magnesium, phosphorus, potassium — as are other whole grains.
Other grain crops with similar advantages include: amaranth, buckwheat, and quinoa. These three grains have no hulls at all, and they are each complete proteins.
If you have a large enough garden (or mini-farm) for growing your own food. Consider trying some (or all) of the above grains as staple crops.