To be honest unless curiosity is really getting the better of you could just start and end it with the 1998 movie. It’s by far the best.
I don’t think any of the sequels come close to it and attempts to just use Sadako as a generic horror monster (Sadako 3D, vs. Kayako, etc.) have been pretty bad.
The American remake is not bad either but it is a very 2000s Hollywood version of the story. I do have a fondness for Rings, the short film that was released as a promo for The Ring Two and also the first half of Rings, the 2017 movie, as well.
But I do think the 1998 movie was a bit of a lightning in a bottle moment that hasn’t been repeated successfully.
If you want to experience the weirdness of the series go to first three novels: Ring, Spiral and Loop. Adaptations have generally shaved off the bumpier edges of the series, even the ones that try to hew a bit closer to the books.
And if you want something that indulges a kind of pop-cultural version of Sadako as a mute ghost who pops out of the TV and is kind of creepy-cute the comic Sadako at the End of the World does this as a stand-alone thing separate from any other part of the series.