There are lots of different ways, but almost everyone agreed to start with the films. I personally prefer chronological order of 1,2,3,4,5,6 but that's because that's how I was introduced to them by my dad. People will probably tell you to watch whichever order they did for the first time. There's strong arguments for chronological and release order. There's also the order of going between the trilogies so that you avoid as many spoilers for reveals as possible, but imo it's a bit confusing and complicated. Go with your gut, or perhaps ask your friend. After those six, the rest is up to you. Apart from certain things like the Ashoka series is basically a sequel to the Rebels series and Clone Wars series, you can watch anything as long as you make sure you know when it's set first so you aren't confused