Amethyst has very helpful how to's in the relay settings. It walks you through which ones you might want to pick under "Relays" in the menu page you get when you click your pfp at the top left of the mobile screen.

 nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z has also written a lot of helpful notes you might search for.