For people who love fossils, ammonites are a great place to start your collection. There were hundreds of ammonite species spanning hundreds of millions of years, and they've been extinct for about 65 million years. They are plentiful, affordable, and many of the specimens are beautiful and in really good condition. Some have vibrant and flashy exteriors that shine like opals, while others may be covered in pyrite (fools gold) or other materials. Other fossils you can commonly find that are relatively affordable include fossilized coral, petrified wood, trilobites, and orthoceras.
Metaphysically, fossils are links to the past, and some people may use them as journey stones for astral travel or to view past lives in meditation.