Instructions
Learn everything you can about gems. Borrow books from the library, look at trade publications, and visit fairs and conferences. You want to learn about how to value the stones themselves, but you also want to learn about trends in the marketplace so you can deal in the gems that are most popular.
Befriend a gemologist. Even if you read every book and article about raw gems, nothing can substitute for the value of experience. A gemologist can tell you in-depth about the quality of gems you are considering purchasing, or about raw gems you are ready to sell. Further, she has contacts in the world of jewelry, which are invaluable when looking for sellers.
Find a reliable source from whom to buy. All kinds and quantities of raw gems are available online, but you want to look first through your personal contacts. It's easy to be cheated when working in this market, so a safe first step is to search for sellers among people you trust.
Make your first purchase. When you've found a reliable source with quality gems available to sell, go ahead and make a deal.
Be prepared to wait it out. The market for raw gems, unlike the markets for other luxury items, is sporadic. You have to be willing to wait for months, maybe years, for a favorable time to sell your gems.