We have to differentiate between the segulos.
There are the segulos based on real sources, and there are the modern segulos that look suspiciously like darchei emori.
The Torah clearly says talmud Torah kenegged kulam.Any segula based on actual learning can’t be bad. Torah is the biggest mitzvah. the biggest lesson of Parshas Haman is found in Rashi Ledoroseichem at the end- Hashem provides our needs. Working is hishtadlus. This is the lesson of Parshas HaMann. On Shabbos, we have lechem mishna to remind us of the Mann. On the day we don’t work, we remind ourselves that we can take off on Shabbos because Hashem provides.
The question is on the segulos that are of recent vintage and don’t seem to be tied into Hashem.
The best segula is always Davening and learning. I am dismayed at the glossy publications promising that if you give money to their organization then you are guaranteed yeshuos. there was an article about this in the yated of 2 weeks ago.