The best way to give advice is to not give advice. Instead, relate a story about something relevant that happened to you. This is called "shared exeriences", in psychobabble speech circles.
"Did I ever tell you about the first car I bought? We took out this large monthly loan, and after three years it was an albatross hanging over our heads when we realized that we could not afford the apartment we wanted because of it. We wound up in a damp basement suite with a mouse and flea problem instead... I gotta tell you, it sucked so much, and we doubled down and paid it off quickly. Thank-goodness. After that, I promised myself to never have a car payment again, and we never have, to this day..."
(ok, so that is my true story..)
The thing about relating a personal experience, is that the other person can take it or leave it, if they think it does not apply to them, and it does not sound patronizing or "I am better than you". It is a just a true story about yourself.