Hi! Previously unmatched student here!
My best advice, especially in the early days of getting your unmatched result, is to be as disarmingly honest as possible. It can feel very vulnerable to publicly announce that you've gone unmatched, but in my experience, it opens up so many connections that you would never have known about otherwise.
When I was unmatched, I made a public F*cebook post, and immediately had support pouring in from family, friends and colleagues. People I had only casual acquaintance with were offering to read over my letters or give me resources to apply to new programs in the 2nd round. It made such a difference to realize how much support I really had.