One thing about Star Trek's universe without money: it's worth remembering that the old european navies used to establish contact with other countries without currency. They didn't set out with money to convince natives to side with the interests of their home empires, they used trade
. This is how the coffee bean (and tobacco) were first introduced to Europe. It wasn't a case of "allow us to use our money which is worthless to you to buy a stake in your country", it was more like "Here are some precious beads from Spain, howsabout we trade them for land in the Mississippi?". Of course, where this all falls down is that old navies usually ended up using guns
rather than diplomacy in order to prosper in a new land. But hey-ho.
Anyway, I assume the "moneyless" Federation exists in a similar bubble. Starship crews establish first contact with races whom they can trade with. It isn't about money
. Even if a planet has got money and Starfleet crews don't, they do
have other resources they can trade. It's through this method that ties are made and treaties signed. Member planets who join the Federation can then give up money, because anything they need can be provided via other means. This is something that the Federation has got good at by the time TNG rolls around. They neither need money, nor do they need to use brute force like the navies of old. * I mention TNG specifically, because it's clear TOS operated on a more 'old school' footing. Kirk mentions salaries for his crew multiple times in TOS, and episodes like "Requiem for Methuselah" show us that, like the navy captains of old, Captain Kirk isn't above using the Enterprise's firepower to force somebody to give him what he needs, albeit he does so apologetically.
I can imagine that the Ferengi, a culture steeped in commerce, are incredibly difficult for Starfleet to deal with, simply because they don't
trade. If something hasn't got a moneytary value, the Ferengi aren't interested in it.