If you buy your ingredients (scrolls & regs) from NPC merchants and resell the scrolls you create, Inscription to GM will actually net you about 100K profit from 49-100. You will have to build up the NPCs to give sufficient quantities of scrolls & regs, but that is easily doable. Just find your favorite mage shops, mark a rune and then recall around getting what you need. Some people use a pack horse to carry extra ingredients, but I never did that. I found I could sit in New Haven mage shop and run between there and the necromancer hut and do ok buying up everything.
Because inscription is profitable from the start I usually train this first on any new shard I begin playing on. Also, if you are starting training, be sure to accept the new player inscription quest. When you hit 50 you will get a "Hallowed Spellbook" which is a basic undead slayer. Might as well get that while you're working it.
Best wishes!
-OBSIDIAN-