According to SemVer, it is good to mark your initial development phase with 0.1.0. Once your project has a stable API or used in production, you can bump the version to 1.0.0.
SemVer was an effort to standardise what each number means in a version.
- If a package version is bumped from 1.x.x to 2.x.x, it means major update and there are breaking changes in the code.
- If a package version is bumped from 1.2.x to 1.3.x, it means minor update and there will not be any breaking changes.
- If a package is bumped from 1.2.1 to 1.2.2, it means a patch which fixes or modifies very minor things like documentation.
For more details, you can checkout http://semver.org/