I divide the theory of mainstream economics into three generations.
The first generation is based on the assumption of rational people and efficient markets.
The theoretical basis of most economists you can see is the first generation theory. Mainly because people will eventually realize their own welfare under limited conditions; Market participants are passive recipients of prices (unless they are monopolists) and so on. Basically, it does not involve competition between several people or companies, nor does it involve the role of information.
The second generation theory is based on game theory and information economics.
Theories in modern industrial organizations, corporate finance, banking and other fields are mostly based on game theory. Will truly describe the market, the internal mechanism of economic organizations. But there are few tests from the real world. Few famous economists in China understand these theories.
The third generation theory is based on experimental economics and mechanism design theory.
Will really use scientific experimental methods to test the theory of economic system. This generation of theories helped society design mechanisms. For example, the auction system, such as the matching system (similar to the college entrance examination voluntary reporting and admission system). China's people who know the theory of this generation rarely show their faces in the media and blogs.
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In fact, how to reach the level of mathematics depends on where we consider it. Different ways can actually draw different conclusions. If you want to learn the most advanced economic theory, you can start from the second generation of economics. Learn game theory, information economics and contract theory. If you just study basic theoretical ideas, it is enough to have the foundation of advanced mathematics and mathematical statistics.