You're stuck on a desert island with 100 people and 1000 units of currency, who gets the money?

The currency would be worthless until there were commodities to purchase. Money only has value as a unit of exchange because we all agree to collectively recognize it as representing a certain amount of labor or materials. The people would first have to organize and build up enough of a society where some of them could specialize in certain tasks, with enough people where they would need a way to reduce their labor to a universally trusted medium.

If everyone knows everyone else, you don't need money, you just negotiate every exchange. Money is only necessary when you don't know who you're dealing with.