Trial and error is necessary, and if you search the forum, you'll find lots of advice on diet, supplementation and stress reduction. For example, if you search under my username, you'll see my posts about diet. A great place to start, especially if your SFN is immune mediated, is here: The Autoimmune Protocol - The Paleo Mom. It has good science behind it and has worked very well for myself and a number of other people who have tried it. Gluten is as bad as it gets, but the Paleo Mom notes all the other offenders. You can try it out and see what you think. It took me 1-2 months to begin seeing real results that I could point to, so be patient, with this and anything you do. Though if some supplement doesn't match with you well, then don't keep at it, of course. I've had bad experiences with a few things and stopped right away. Positive results are different and everyone is different to some degree, so it takes time to see what, if any, positive results you may have from diet, supplementation or any lifestyle change.

Good luck!