Just made this simple diagram to explain how free & paid relays work. You can see the trade-offs of using only free relays: less discoverabilities by others, and a completely useless global feed. At the very least, you should add global feeds from paid relays (they are still free to read), so that you can discover other content. If you want other people to discover your content (people who don't follow you directly), you should pay for at least one popular P2W relay.