It was common. After Pompey Magnus and Marcus Licinius Crassus crushed Spartacus, ending the Third Servile War (73 - 71 B.C.E), it's been estimated that around 6000 prisoners were crucified along the Appian Way.

Arrian (a Roman historian) claims that Alexander the Great crucified people as well (hundreds, if not thousands after taking the city of Tyre), and he supposedly got this information from material left behind by Ptolemy, one of Alexander's top generals.

Herodotus describes the execution of a Persian general at the hands of Athenians in about 479 B.C.E: "They nailed him to a plank and hung him up ... this Artayctes who suffered death by crucifixion"

I'd also like to quote the following;

"This form of state terror, widespread across the Roman Empire which included Europe, North Africa and Western Asia, originated several centuries before the Common Era continuing into the fourth century CE when the practice was discontinued by Constantine, the emperor of Rome. Hengel, in his monumental work on the subject, Crucifixion (1989:22-23) writes that while authors generally regard it’s origin as in Persia due to the writings of Herodotus it’s practice was found among the Indians, Assyrians, Scythians, Taurians, Celts, Greeks, Seleucids, Romans, Britanni, Numidians, Carthagians the latter who may have transferred it’s knowledge to the Romans." - Crucifixion in Antiquity: The Archaeological Evidence, by Joe Zias