My source for collecting is usually the farmers market. Yes, I have used BrickLink, it’s good, but I can get lots of G1 sets for awesome prices because people don’t know what they are worth. Same goes for second-hand shops like Value Village and Goodwill, and things like garage sales. Although, the condition of the sets may be more damaged than BrickLink. I guess it all depends on how serious you plan on getting into collecting.