Usually, Id recommend only buying one as a casual player, but their comparably low price means it may be a good option to both so you can try each and play with people who dont have their own decks
Note that "face down" is not synonymous with "with its back face up." A manifested double-faced card is a 2/2 creature with no name, mana cost, creature types, or abilities
When properly utilized, these cards greatly place the odds in their owner's favor, making the game less about strategy and more about who draws their powerhouse cards first
That said, context changes the answer to this question
Because the difference in price between a 1 st Edition and Unlimited card can be so significant, counterfeiters often attempt to add 1st Edition stamps to legitimate Unlimited Edition cards (cards released after the 1st Edition run of a set)