IMHO you should consider to add relays of well known clients (most of them are running own relay) as...

wss://relay.damus.io
wss://relay.snort.social
wss://relay.plebstr.com
wss://nostr.rocks

also aggregators like these make some sense to me...

wss://purplepag.es/
wss://relayable.org

then you can consider adding some paid relays that bring a special feature or will be more persistent...

wss://filter.nostr.wine
wss://eden.nostr.land
wss://relay.nostriches.org