It's cool to see younger people are interested in these old games still.
Gold/Silver/Crystal are based on the Red/Blue/Yellow engine, so it'll be familiar, but they made so many changes to the mechanics and added many new features such that it feels like the original games on steroids. I played Silver first, so going back to gen 1, it was kind of shocking how primitive it felt by comparison, even though it's basically the same hardware. One of the craziest features at the time was the real-time clock in the cartridge that allowed for a day/night cycle and keeping track of the day of the week, so that in-game events could occur on a weekly basis. Unfortunately this feature doesn't work on some emulators. It's not required but it definitely adds a lot to the experience.
While all games in the second gen are good and Gold is certainly a fine game, I might recommend playing Crystal over it due to the new story elements and features it introduced such as the Battle Tower. Also, Crystal has this fantastic battle theme for the legendaries that Gold/Silver don't have:
https://www.youtube.com/watch?v=Y_ZoaAtajiU 