One of the older "life hacks" is to put a teaspoon of vanilla extract in the oven to make the house smell better. Speaking from experience: don't use more than that or you will regret it. I couldn't visit their house for a week.
[0] https://moneyweek.com/chart-of-the-week-vanilla-could-soon-b...
It's a cooking joke, because vanilla is incredibly strong.
I said 5 plants because it's the fewest needed to be able to split out 80% without fractions.
You obviously need to eat some other stuff occasionally, but those plants are the staple diet for a large chunk of the world population.
I'd need some variety just so I didn't go insane.