Work one's way up

어떤 과정에서 점진적으로 진척이 나아지다; to make progress in a process or structure; making progress and advancing.

• Mike and I, we worked our way up from the mailroom.
• Just look at Johnson if you need proof: He started in the mailroom, but worked his way up to one of the top lawyers at the firm.
• He started as an office junior and worked his way up through the company to become a senior manager.