Chromatic Orb is a commonly taught spell for young wizards, but not-so commonly used.
When an evoker first studies The Art, they usually start off learning how to use different cantrips and familiarizing theirself with the different “elements” of magic. Fire Bolt, Ray of Frost, Shocking Grasp, Poison Spray, Thunderclap, Acid Splash, ETC. After a year or more of this, a beginning Evoker must put everything they’ve learned about the elements together and a perfect Chromatic Orb.
After they’ve passed the test, they likely won’t have to again.
This is because among most students of The Art a 50gp Diamond represents 50gp they’d rather spend on fancier hats, more advanced texts, and fruity liquor suitable for those with dumped constitution scores.
For this reason, every University of The Art is equipped with a very profitable “Arcane Shoppe & Rentlle” boutique. Among other texts and foci, students can rent cracked, opaque diamonds that look as though they’ve spent more time at the bottom of a Wizard’s backpack than in the ground.
Advanced Evokers with a blind spot in personal accounting typically cast Chromatic Orb without the diamond. The only drawback to this is that the damage type for the orb is completely random. In other scenarios where diamonds are in short supply (cough cough revivify cough), a different gem can be used to cast this spell -- although only one damage type can be produced:
Ruby (Fire)
Pearl (Acid)
Sapphire (Cold)
Jade (Poison)
Amethyst (Thunder)
Topaz (Lightning)
In the hands of an Evocation Savant, Chromatic Orb cast at the 9th level produces similar effects to “Meteor Swarm.” Except there are six meteors (each one inflicting one of the six damage types in addition to bludgeoning damage) and one of the meteors is centered on the focus, shattering it instantly.