Who bought the very first car?

There's no single answer to who bought the very first car. It depends on how you define "car." There wasn't a sudden, universally agreed-upon moment when the first car was created and sold. The development of the automobile was a gradual process.

Karl Benz is generally credited with creating the first practical automobile, but he didn't sell the first one to a person who would consider it in the modern sense of personal transportation. His early sales were more akin to selling a new type of engine.