Very plainly put, you want a large middle class, and a rotating lower and upper class, with the various aggregate metrics from min to max, and everything in between to rise over time.

In that state, you want to enlarge the pool of people whose lifestyle affordances are more and more similar to one another, and since no one is poor for too long, or rich for too long, they don't enshrine themselves as some systemic class of people forming clicks, bad habits, group identity of them and the others, falling into self-selection and preservation, or some vicious cycle that entraps them there, etc.