You do not need Part 107 to begin training, building workflows, or preparing your business plan. But if you plan to charge for drone work in the U.S., commercial operations generally require a Part 107 Remote Pilot Certificate. A smart path is to train and build your offer while preparing for the exam so you are ready to take paid work as soon as you are certified. If your immediate goal is passing the FAA Part 107 exam, get the FAA 107 Study Guide here: https://faa107studyguide.com.