Fig.: to gain experience and learn skills by starting at the lowest level available and then working one's way up 

Today he's the editor-in-chief of a major international newspaper, and to think he learned the ropes by proofreading his high school student publication

Oggi è il direttore responsabile di un giornale internazionale molto influente, e pensare che ha fatto la gavetta correggendo le bozze del giornale degli studenti al liceo

Diana is a Broadway star, but as a young soubrette she paid her dues in dozens of small-town theaters

Diana è una stella di Broadway, ma da giovane ha fatto la gavetta in decine di teatri di provincia 

A nautical term, from the old days of sailing vessels. A three-masted ship had over 200 ropes, each having a specific name and function. New sailors had to memorize the name and learn how to handle each rope, so that in an emergency situation – such as a storm – they could manage the right rope in the right way without hesitation