Having graduated in communication from the Warsaw Institute of Technology, Gmoch became a football player and started playing for Znicz Proszków, until later on he started on a successful run for Legia Warszawa. Within Warszawa, he won the Polish Cup twice (in 1964 and 1966) and contributed to the beginning of the successful 1968-1969 season.
Following a minor injury in a friendly match, Gmoch began a coaching career, starting in Legia Warszawa in 1969-1971. Having been offered the assistant's job by Kazimierz Gorski, he lasted from 1971-1974. He later moved to Argentina in 1978, to Norway in 1979 and Greece until 2003.
In Greece he coached Apollon Athens, AEK, Panathinaikos, Olympiakos and AE Larisa which, under his guidance became the first Greek club outside the Athens-Piraeus or Thessaloniki metropolitan areas to win a championship.
Gmoch acted as a member of the Polish Olympic representation team in 2004 and later became a minor shareholder of Legia Warsaw, as well as following up a career in television commentating for several networks.
Gmoch holds both Polish and Greek citizenship.