The nice game design with this game is that how much you lose by flipping the vampire is scaled to the numbers of cards you flipped.
So if you only flipped one card and got a Vampire, you got unlucky and only lose a small amount, while if you almost flipped everything, you lose a big amount (which is more likely because you played bad/gambled).
You should try to Pass more often when you're not sure but you're still getting a positive income. And you shouldn‘t flip unecessary cards so the stake Bonus is higher (ex: if you know a card is 2+, you don't need to flip it, you already know it's very low, this way the Stake bonus is higher if you find the Vampire quickly).