Sorry to break it to you but it’s no longer viable to just have 3-4 passwords to memorize or simply add small changes. With the exponential rise in computing power and data breaches, brute-forcing and rainbow tables are increasingly viable.

Just memorize a ridiculously strong password (I recommend a combination of a quote/passphrase and made up words in addition the standard best password practices) and use that for your password manager. Bitwarden and many others have a password generator where you can generate 30+ character passwords