The duplicate question:

Q: Im trying to cast chromatic orb on some goblins, but I dont have enough mana. Is there any way to make it use less?

A: You shouldnt be using chromatic orb on Goblins, you should be using eldrich blast.

"Op is saying eh doesnt have the mana to cast chromatic orb, eldritch blast uses 3x as much mana and is way more complicated to use"

"Well theres a reason no one uses chromatic orb, OP needs to learn best practices."