Per the Narrator section (Autumn, p.70), the pool for awarding Dreams is common and shared by everyone at the table, including the Narrator, who is encouraged to take the lead in awarding them to the players.
Dreams are, strictly, just a number on your character sheet and not actually represented by any kind of counter, but using a pool of counters makes tracking them more convenient and breaks the flow of play less.
Dreams are "applause" for good "acting", and it's much less disruptive for the person who's "applauding" to grab a chit from a common pile and slide it across the table than it is for the person who's "acting" to stop and write down that someone clapped.
The narrator advice is that you provide a big pile of Dream tokens so that you can keep using the more convenient method over an entire play session. If the pile happens to run out you can keep an additional tally until they're spent or pause play and everybody pitches back 10 or whatever and writes "10+" on their character sheet, but either way that's a little disruptive. I'd advise cutting up note cards or buying a bunch of cheap glass or plastic beads.
Ultimately the only restrictions on Dreams are:
- you can only award one per character per "action"
- you can't award them to yourself