I generally recommend keeping about 10-15 tops. Paid can make up half or better. Especially with the filter to keep you in touch with free relays.
More than that really burns your battery up for no real gains.
You can extend your reach by going to nostrified.online and blasting out your events every so often. Make sure to show #[4] some love for the tool.
I also vet my relays through nostr.watch to see how fast/slow they are. If they’re slow they’re either too far away or too loaded. We contribute to the decentralized nature of nostr by spreading out some.
You only need one shared relay with someone to see their notes.
Just some general tips.