first learn all you can about epidemiology, causes of chronic disease with little or no expenses.
also develop your skills in critical thinking. Look for the most cost efficient ways in every area. avoid programs dependent on grants, tax payer dollars and bureaucracy.
Explore the evidence based prqctices of lifestyle medicine , neurobiology based coaching and the most simple answers to minimize, prevent and reverse diseases. Practice these skills in your own life as you humbly address the challenges in behavior changes. Develop a servant heart in your own community as you do menial tasks that meet people face to face, and listen to learn.
Learn from those on the frontlines like at www.lifestylemedicine.com and wellcoaches.com
There is no advanced public health nurse or certification. However, you can try to apply for public health nurse position and try to build experience to go up in the ladder