Contrary to what people suggested, I would advise against optical discs or tapes and would go with HDDs you check every few months. They don’t rot like optical media, the only thing you have to worry about are the motor spindles getting stuck and other mechanical failures.
It will also be the cheapest option. With tapes you need expensive drives and they change the version every few years. Tapes only are better if you store hundreds or thousands of TiB of data.
Which data so you want to save? Mostly games and media? If so, consider giving them to your friends and family to copy and enjoy, which some people call a ‘friend backup’.