Is it wrong for a Jew to say “I’m keeping my fingers crossed” for good luck? And if so, is there a Jewish equivalent to crossing fingers? I’m waiting to hear back about a job interview, and need all the luck I can get . . .
Yes, it is wrong for a Jew to cross his fingers for good luck. The Jewish equivelant would be giving extra charity, saying a prayer and the like.
Placing belief in any other supernatural power other than G-d is contradictory to Jewish belief. Even praying to angels is forbidden, we place our trust in G-d alone. We do find in the Talmud a number of seemingly “superstitious” practices, such as eating certain foods at the beginning if the new year [Horayos 12a], getting married on certain days of the week [Kesubos 2a], and others.
See Shulchan Aruch Y:D 179:2, the Commentaries there explain that there is a difference between “Nichush” which refers to trying to decipher the future based on unnatural means, and “Siman” which refers to doing things at auspicious times and in a positive light, which is permitted.
Crossing fingers would seem closer to the first, trying to ward off “bad luck” by unnatural means, and should be avoided.