I always recommend using a password manager. The issue is that you need to use a password to access the password manager! And you can’t use the password manager to enter it.
Standard recommendations are for complex passwords like xT8&oP9MUWdui0!L. But that is impossible to remember and very hard to type in correctly. The good thing is that it should take centuries to crack.
Recent thinking is to use four or more words that you can remember, like ‘take pills horse strength’. Sounds counter-intuitive that it is more secure, but this should also take centuries to break but not centuries to remember!