An Instant Win Reindeer is a guaranteed win, provided that your participation is in accordance with the rules.
Collections are sets of matching flaming reindeer (same type, level "white", "silver" and "gold") that must be collected in order to win: any complete collection is a win! You'll collect many Flamedeer throughout the event, and can trade with other users if you collect any duplicates.
This means that there can be an unlimited number of "white" and "silver" reindeer, but only as many "gold" reindeer as there are prizes.