The velocity dispersion of gas within galaxies is typically 30-40 km/s. Stars are born in gas clouds. But later on, their orbital velocities reach several hundreds of km/s. How is this possible? Where and how do the stars gain their angular momentum and their final orbital velocity?
The velocity dispersion of giant molecular clouds in the vicinity of the Sun might be 30-40 km/s (this sounds too large to me actually), but their orbital speeds are of order 220 km/s, like the Sun.
The velocity dispersion is the spread around an average value. The orbital speeds of stars are similar to the clouds from which they were born.