A few years ago, vintage jewelry was much easier to find in places like thrift stores and much less expensive. Now what I can find for a reasonable price usually has some flaws. I get past that by restoring the pieces.
The worn finishes can be touched up with gold or silver nail polish.
I can brighten up pieces missing small rhinestones by using glitter glue, then applying silver glitter and removing the excess.
You can pry out old rhinestones (of the right size) from rhinestone buttons to replace larger missing stones in jewelry. Just glue in with superglue.
You can also replace broken pin backs with well-placed safety pins or pin backs from the craft store.
And, of course, you can fix broken links by using a pair of pliers!