"Here are my experiences training Inscription from 50.0. Note that my goal was not to train to GM in the most efficient way possible, but rather to have usable materials at the end.
400 attempts at Recall - 50.0 to 67.1
400 attempts at Mark - 67.1 to 79.3
573 attempts at Gate Travel - 79.3 to 100.0
All of this was done with 40 NPC-bought scribe's pens. I had several left over afterwards.Total cost was less than 30k gold."