Kitchen scale - most artisan bread recipes are measured in grams - cups just aren’t exact enough. I use my kitchen scale all. the. time. Here’s the one I have.
Kitchen Aid Stand Mixer with dough hook attachment - You don’t really NEED this, but I’m not gonna lie it makes life so much easier.
Large glass bowl - metal or ceramic are also fine, I personally prefer glass because I can see dough development and glass retains heat better than metal
Banneton proofing baskets - to start out, you can proof your loaves in any old medium kitchen bowl with a clean kitchen towel and lots of flour - but if you keep up with it you will want some of these eventually. There are tons of different sizes/shapes on Amazon.
Lame - to start out, you can use a sharp kitchen knife - but if you want to make fancy shapes in your loaves or just get a smoother, cleaner line you’ll want one of these eventually. Both the banneton baskets and the lame are inexpensive - it’s more of a commitment to more kitchen gear that you may or may not use than anything. If you’re certain you want to start making sourdough somewhat regularly - def get them. Here’s the lame I have.
Dutch oven - unless you’re lucky and have a steam injector or proof setting on your fancy oven - you’re probably gonna want one or two dutch ovens. I have two because I bake two loaves at a time. We also obviously use our dutch ovens for tons of other stuff, they’re very handy.
Baking stone - alternative to the dutch ovens, you can try using a baking stone and spraying water in your oven to produce steam. This did not work at all for me, but everyone’s environment and set up is different. I actually use dutch ovens on top of a large baking stone for an extra source of heat.