From what was implied in one of the episodes, it seems he was a successful businessman with a good reputation on what could be the legal and illegal side of things. In the episode where he's meeting Don Eladio with a young a partner, Gus was playing the role of the venture capitalist, the money man, with an investment (the chemist). It's possible he worked in Chile for a subsidiary of that German conglomerate that owns his chicken brand. Also, I wouldn't exclude the possibility that his story to the DEA agents wasn't all lies. It could be possible he had ties at a local university where he could have met the young chemist.
I don't think he was a drug lord at that time simply because he was very nervous in that initial meeting with Don Eladio. He seemed like he was just entering the drug game and trying to apply what he knew in his past work to the operations side of drug distribution.