Hill Workouts - How to know if successful

I’m trying to incorporate hills in almost every run for NYC Marathon training since that is a major piece of advice i hear from almost everyone.

Is there a rule of thumb of what can be considered a hill workout? How do you determine what is a good hill workout or not based on total elevation gain? I’m doing most of my runs in Central Park but would love to know if there is a standard of measure for overall elevation gain.

For example a run like this:
12 miles at 367 ft elevation gain