Mishna Berurah – all 5 Chalokim. Learn it, and know basic halacha very well.
Really easy segulah.
As a side note, there is a segulah in the aseres hadibros. Kabed es avicha v’es imech lmaan yarichun ya’amecha.
No kupat ha’ir “guarantees” needed. Straight from maamad har sinai.
Pretty simple.