If you're looking to safely get OSRS Gold, it is crucial to select a trustworthy one. In general, if look up "OSRS Gold" directly on Google there will be several Third-party platforms for trading. The ones listed on the main page are typically more secure.
However, this isn't an absolute fact. According to me, for those looking to buy low-cost and safe OSRS Gold, the best site is suggested by a friend. I generally go with the RSorder website, as I've been using the website for the past three years and I've always been confident in RSorder.