1. The First Amendment:
The First Amendment is by far the most important on the Bill of Rights, as it outlines the primary rights that people have in the US. It ensures freedom of religion, freedom of speech, freedom of the press, freedom to peacefully assemble, and the freedom to petition the government. These are the most basic liberties, and especially these days they have come under question regarding the extent of their meaning.
That concludes the list of the most important amendments in the Bill of Rights. Hopefully it gave you an insight on how the government functions and what the most critical points of primary documents are.