Is it true that you can't draw spells without offering sacrifices to your ancestors?

Yes, without a teacher, you don't know spells, tactics, courage and so on. In ofuda, and there will be at most one calligraphy work, which is invalid.

As the saying goes, "I don't know how to draw, but I make ghosts and gods laugh;" If you can draw, you will be surprised by ghosts and gods. Of course, there is also a saying that "drawing does not attract ghosts".