I use to have about 15. After this update in this client i'm on you just add relays automatically when you follow people I know have over 1600 relays. So I see a lot of stuff & reach out to a lot of people. Some relays mirror other relays npubs so I see some stuff 2-4 times.

It can be excessive but if you want to grow your content having more means you reach out to more people when you post something. So seeing what you mainly put out I think you would want to add as many as you can & just deal with the spam on global feed as you go. Remember every client handles that web of trust me bro I told you about remember?