In several principles-of-economics textbooks, the first chapter is devoted to the basic elements of economics such as scarcity, tradeoffs, opportunity costs, incentives, marginal thinking, etc. Most instructors spend very little time with this chapter.
I spend weeks on these concepts. These principles are at the heart of economics, which is, essentially, the study of human behavior.
...I don't use graphs to illustrate the concept of tradeoffs. Instead, I have my students look at data such as the real-world military spending as a percentage of GDP of North Korea. And then we look at a satellite image that suggests some implications of these data. If you haven't seen it, check it out here...The North Korean government has made a tradeoff between guns and butter.
I probably will be teaching a high school econ course next year. I like to have students work out the arithmetic of starting their own business--so that they can understand labor, rental cost of capital, and the challenge of making a profit.
I'm also thinking of working really hard on basic economic concepts. One thought I had is to have the students write short papers explaining in their own words the concepts of comparative advantage, opportunity cost, and such.
I know a lot of teachers like market simulations, so I might consider that.