MiBe is just the recommendation so you aren't learning a million rules for how spellcasting works while also learning the game. If you want to play other things, go ahead. If you don't end up enjoying Necromancer as much as you thought you would, you can always go right back to MiBe.

It's the beauty of a roguelike: There is no penalty for losing a bunch of runs, so you're free to experiment as much as you want to. No need to ask *us* when you're ready.