Today our phrase (and gesture is), cross your fingers.
This means you are hoping for good-luck. If you use the gesture itself, then you don't have to say, cross your fingers. Why? Because all Westerners understand the meaning. You make this gesture by crossing your middle finger over your index finger.
I bought a lottery ticket for the huge jackpot this weekend. Fingers crossed!
I submitted my application to Tokyo university. Fingers crossed I get accepted.