If there was a chart of this kind of thing or a solid non-SEO-spam resource, that would be helpful, too.
Seconding tomatoes. You may need a tomato cage or a couple bamboo poles and string to support the vines but nothing fancy. They grow well with basil too.
If you like hot peppers, grow them too- and make your own easy salsa.
The answer to “what cuts my grocery bill” raises the question of what groceries you buy. In general, small-scale farmers/gardeners who make a living off a limited plot of land tend to gravitate to leafy greens, because market prices give those the most revenue per square foot.
Seconding herbs but grow your mint indoors. Rosemary (once established ), thyme, and dill are consistent and useful to have around.