Just about any black ring will do. There's a variety of black rings available for sale on Amazon, Etsy, eBay, etc. Your local jeweler may have something that fits your tastes and budget. Black silicone rings seem to be quite popular, too, as you can wear them to the gym, beach, pool or hot tub and not worry about accidental damage.

That's largely up to you. If you are full-time non-monogamous or open to a variety of partners at any moment, then maybe you should wear it all the time. If you're only open in certain situations, like play parties, clubs, vacations, etc. or only when you and your partner are together, then consider wearing the ring only when you're open to meeting new friends.

Can't say for sure. Do you appear friendly and approachable? Many factors go into whether people will engage you in conversation, flirting or play / scene negotiation. The black ring on your right hand isn't magic. You may need to do some of the work yourself.

A black ring worn on the middle finger of the right hand is an infrequently used symbol of asexuality. Please avoid wearing your ring on this finger as a courtesy to that community.

Technically, that's not a question. But here's an answer anyway.

Sure, it's real. So says the New York Post, these kind folks selling swinger jewelry, a bunch of Etsy shops, and a variety of super old blog posts from the early internets. (No affiliation or endorsement implied with these links.)

Yup, that's still a swinger symbol, too. There are a variety of signals sexy people have used over time. Sometimes seen on clothing, jewelry, flags and other merch, pineapples abound in the swinger community. But, pineapples don't fit everyone's style. Some may prefer a black ring instead. If pineapples are more your speed, then do that. To each their own. Just be cool about it and have fun!