One of the characters wants to be a lightspeed pilot. This is an elite group that only a very few have the right physical and mental qualities. The story is about that character's obsession. Another character has a crystal globe with a self contained ecosystem.
This might possibly be Samuel R. Delany's novella "The Star Pit" (1967), readable online at archive.org. Two of the main characters, the protagonist Vyme and Ratlit, have knocked around the galaxy before settling at the Star Pit. Only a small group of people, called "golden", can travel outside the galaxy; others all go insane:
But as a ship leaves the galactic rim, 'reality' beaks down and causes insanity and eventual death for any crew ... Some few of us whose sense of reality has been shattered by infantile, childhood, or prenatal trauma, whose physiological and psychological orientation makes life in our interstellar society painful or impossible — not all, but a few of these golden . . ." at which point there was static, or the gentleman coughed, ". . . can make the crossing and return."
The name golden, sans noun, stuck.
Ratlit envies the relative freedom of the golden:
"Oh, Vyme, the places he's been! The things he done, the landscapes he's starved in, the hells where he's had to lie down and go to sleep he was that tired, or the heavens he's soared through screaming!..."
The globular ecosystem also appears, as well as other self-contained ecosystems:
Some blue liquid, a fairly large air bubble and a glob of black-speckled jelly in a transparent globe, the size of an eyeball; it was set in two metal rings, one within the other, pivoted so the globe turned in all directions. Mounted on the outside ring was a curved tongue of metal at the tip of which was a small tube with a pin-sized lens. The tube was threaded into a bushing, and I guess you used it to look at what was going on in the sphere.
"Self-contained," explained An. "The only thing needed to keep the whole thing going is light. Just about any frequency will do, except way up on the blue end. And the shell cuts that out."