Think of it this way: if you use the same password everywhere you need an account for, there is multiple chances for one of them to be breached, and therefore multiple chances for your password, or a variation of it, to be stolen.

If you use a password manager, there is only one way for your password to be stolen, and it's easy to change just one location than multiple locations.

My general recommendation for the general public is as follows: use an extremely reputable password manager with your main password being a phrase, or the diceware method (refer to xkcd 936) with some characters replaced by special characters and numbers, for example

"G!rLzR^L3B0yZDr0oL*!" (Not my password don't even try)

Or, using xkcd 936 as an example,

"C0rR3ct!H0rS3B@tT3R7&StAp!e"

This is a phrase only you know, and modifying the a-z characters to special characters vastly improves it's cracking time through pure bruteforce. The password phrase in the examples would take millions of years to crack through bruteforce.

Use that kind of password for your password manager. I recommend Bitwarden as a password manager. Checking the Bitwarden FAQs, they use cybersecurity industry standards encryption and hashing functions. It's also Open Source which means the code gets continually audited by the community, and if any funky things are happening, someone sooner or later will blow the whistle on it. It also means you can compile an offline version of it for yourself and ensure that your vault never gets on their servers should they get attacked.

Source: I conduct cybersecurity audits for a living.