Full many a gem of purest ray serene, The dark unfathom’d caves of ocean bear:
Ways of Reading: Gray uses the metaphor of a "gem" to perhaps describe people who have unrecognized, positive qualities, likened to undiscovered gems in dark caves at the bottom of the ocean. The next lines continue this idea as well, using yet another nature metaphor(flowers unseen) to describe the unappreciated beauty of some people, with "sweetness wasted on desert air. This could also harken back to Gray's allusion to classes and the "penury" being suppressed by the nobility. https://www.enotes.com/topics/elegy-written/in-depth