In fact, if you spend 1 week for faucets, then you can buy level 1 or level 2 mines. Theorically it counts as "investment", but in reality you aren't really "invest".
My advice is, gather 200K satoshis from faucets and buy a level 2 mine, then enjoy the game.
My advice is, gather way more than that from faucets, invest in a level 5 mine, and use those earnings to buy the lower level mines. Start at the top and work down.