Dr. Axe on YouTube talks about how to heal autoimmune, and on his website writes about how to heal leaky gut. They go hand in hand, because healing leaky gut is one of the first steps for healing autoimmune.
First remove the things that causes inflammation and leaky gut such as sugar, hydrogenated oil, omega-6, gluten, and casein.
Then add more cooked vegetables to your diet. For autoimmune, too much raw may not be such a good thing because they are harder to digest. And some fruit, wild-caught meat and salmon (for omega-3).
He is a big fan of bone broth. While authentically bone broth either store bought or made on your own is preferred, he does suggest Ancient Nutrition Bone Broth protein powder if you can not make bone broth on your own (in this other YouTube video).
And he said that coconut oil is one of your go-to cooking oil.