While 1,000 words allow you to survive, 20,000 words allow you to thrive. A vocabulary size of 20,000 words is roughly the size of a well-educated native English speaker's passive vocabulary.
To give you an idea of what you will study, here is a micro-sample of how a serious PDF organizes data: --- 20 000 Most Common English Words With Meaning Pdf
This goes beyond a simple list; it outlines the specifications for a premium, educational, or reference-grade document. While 1,000 words allow you to survive, 20,000