like everyone else, start off with a basic set and add as you build experience and learn about how you work. 36 years ago I started out by buying cheap but vary durable Stanley chisels. So the first set assembled was a 1/2, 1, and 1 1/2 inch, and added a 1/4 later when I started chopping mortices. At present I have 36 that range from 1/8 up to 1 1/2. They include the original 1/2, 1, 1 1/2 stanleys I first bought (the 1/4 died a premature death by getting snapped off in a mortice).

A basic range that I could easily get by with are 1/4, 1/2, 3/4 and 1. The 1/4 will fill the shoes of a 3/8 and the 1/2 fill in where a 5/8 would be more suited... It's nice to have a 1/8 and a 1 1/2 but I could easily taylor my work to avoid needing the 1/8 and the 1 would not be quite as good as the 1 1/2 in certain situations but would be adequate. In 10 years you'd most likely have triple the number you started out with...