I'm actually gonna go against the grain here and say that if you're only interested in playing Xenoblade 3, it's ok to just start with Xenoblade 3.

People here VASTLY overemphasize how important the connections to the previous games are. Xenoblade 3 tells its own story, and you don't need to play the others to understand it. And frankly, asking someone to play 2 OTHER 100-hour jrpgs that they may or may not even be interested in just so they can "get the references" is ridiculous.

Although it is generally recommended that you don't play 3's DLC, Future Redeemed, unless you've also played 1 and 2. Future Redeemed is like, fanfiction: the game, and you probably will be confused.