"Food Families" is a term I use to indicate Food-from-region-of origin. I feel that "ethnic" doesn't fit, because...well...look at Chinese cuisine. When you say "Chinese cooking," what regional (or ethnic Chinese) cuisine are you referring to?
"Family" references the relatedness between different regions without lumping groups into an "ethnic" category they don't belong to. (Anthropologist-in-training showing here :P)
After you have maintained a food diary for two weeks, you should start to notice that your choices fall into broader categories.
For instance my own are: Asian, Mexican, and Italian-Mediterranean.
Now that's a wide variety, but it informs me what oils, seasonings, sauces, and grains I need to keep at hand.
Each "Food family" has different-but-related base seasonings. (This is a result of geography, trade, Imperialism, etc) Basically, you have an array of tastes for each of your food families, and "ethnic" options underneath that umbrella.
So you have key items that you keep stocked, because these will allow you to construct meals from any of your "food families."
How do you find out what these ingredients are?
Start with your favorite dishes. Pull up their recipes. Set the recipes side by side. Now take a pen or pencil to the list.
If you have repeating ingredients that show up in at least 2 of your recipes, circle them. These are your stock items, and some of the first things you should buy before meal planning.
Obvious ones are soy sauce for Asian cooking, olive oil for Italian cooking, wine for french cooking, cream and salt for American cooking...
But there are more seasonings and spices than the "obvious" ones. And sometimes these even "cross" families. Like basil, sherry, honey, garlic, onion, salt, sugar, and canola oil.
If there is a seasoning option that you can use "in place of" another ingredient, and the replacement ingredient is in line with other dishes--use the replacement. This means that you keep that "replacement ingredient" on hand, and maintain you "stash" effectively.
Effective management of these base ingredients makes all meal planning possible.