This phrase first appears in Shakespeare's play The Merry Wives of Windsor
Falstaff: I will not lend thee a penny.
Pistol: Why then the world's mine oyster,
Which I with sword will open.
Falstaff: Not a penny.
The oyster contains a precious pearl which attests to itself high value, even today. If the world is one's oyster, they have the chance to seek high rewards. You may have access to many opportunities to leisurely choose from, given that you are in a position to do so. Those in North Korea would may have oyster intolerance.
Fuck the economy, I want an oyster.