Every human group, even those who live in tropical areas, where all foods are abundant, have staples. A selection of one to three foods that they eat daily, in calorifically significant doses and all year round (or pretty much so).
They may be staples by a small margin, such as some areas of India where 'legumes' are the staples and no specific legume is consumed all year round; or staples by quite a lot, such as three certain Japanese populations, whose native diet was 70-80% sweet potatoes, glutinous potatoes and yams, respectively or the Inuit, whose staple is seal.
A staple has to fulfill at least two of these requirements:
-be consumed through most (or all) seasons
-be consumed daily
-forms a significant portion of your yearly kcals
-is from a specific food source (so: "all varieties of pea" counts, whereas "fruit" does not)
So, what foods in your diet would fit the category of staples?
Mine: potatoes and butter. Everything else changes based on the season, but I'm always eating potatoes and butter. Pretty much daily too. Definitely the bulk of my yearly kcals.
For fun, I worked-out those of the SAD. Basically: construct a SAD day's worth of meals, list the ingredients, the number of times they appear and the kcals they contribute. Select the three that fulfill the role of staples. You'll find they are wheat, hydrogenated vegetable oil and dairy.