No Man's Sky/Money-making/Rare resources

One way to get many units is to collect rare resources from planets. However, some are dangerous to get without taking damage, like living pearls. Others are in dangerous places, like albumen pearls. And some, like gravitino balls, summon sentinels when taken.

Tips

 * Look underground, in caves for humming sacks.
 * Look for clams underwater. Shoot one to open it, then quickly take the pearl before the clam closes. Don't get too close, as clams deal damage when they close.
 * You can get gravitino balls in planets with high sentinel activity, but be warned: taking one will immediately anger sentinels and increase your wanted level to 3.