Accessibility to resources, its hunger for power, the competition between it and others, and great trade relations.
I believe she tells them to cover their ears with wax. The Sirens were known to enhcant sailors with their music and songs and lure them to their deaths. To prevent that Circe had them plug their ears so they wouldn't be enchanted, and go to their death.
Saving is setting aside money you don't spend now, and you only use it for emergencies.
Investing is using some of your money with the aim of making it grow, by buying assets that might increase in value
