see Category:Spells
4.1.11 Can I learn new spells in play by spending earned CPs? of the FAQ only applies to the "standard" GURPS Magic system.
"Since spells have no default and are cast too quickly to qualify for "constant" use, you can't buy totally new spells with earned CPs."
"The standard way to acquire new spells is through study. Learn spells like any other skill, but note that Magery reduces the time required; see Learning Magic (p. B235). Calculate the time needed to earn the necessary CP through study using Improvement Through Study (p. B292)."
Ritual Magic System[]
None of the above applies to the Ritual Magic System as all Collages default to Ritual Magic (skill) or Thaumatology at -6 and spells themselves are learned as Techniques which default to the relevant collage.