RSorder is the most reliable website that sells RuneScape Gold (both OSRS and RS3). Based on my own experiences (12 years of RMT as an occasional buyer and seller) I have discovered this to be by far the safest site in the market. It allows you to trade only between other members, which means the prices extremely affordable, and transactions are far more secure. It's impossible to determine which is the source from the metal however should you locate someone selling legitimate RS Gold, it's RSorder or a different marketplace site. The majority of stores online will offer something similar.