Gluten-Free does not = healthy in all cases. There are a lot of gluten-free foods out there that are just as bad or worse for you than the white bread/bakery stuff. So read labels, look for whole grain gluten-free products (brown rice & pasta made from brown rice, and other gluten-free whole grain products made from oats, quinoa, millet, etc.).
Some find they need to omit all grains.
Some find they need to omit most non-vegetable source carbs.
Some find they need to omit nightshade vegetables (bell peppers, tomatoes, eggplant, potatoes - sweet potatoes are ok, they are in a different botanical family).
Some find they need to omit sugars (including fruit).
Some find they need to omit yeast (fermented foods (cheese, etc.), yeast breads/bakery goods, yeast extract added to packaged foods, etc.).
Some feel best on the Specific Carbohydrate Diet (Google SCD and you'll get plenty of info on this diet).
Some feel best on the Paleo Diet (
http://paleodiet.com ).
Some find they only need to eliminate gluten & dairy (gluten and casein are pro-inflammatory proteins).
Some find they don't need to eliminate anything, but their progress may be slowed. Sugar in the diet contributes to yeast/Candida overgrowth, and being on Lyme treatment with antibiotics also promotes Candida overgrowth.
IMHO, blood type, specific infections, treatment options (abs vs. herbal), lifestyle, allergies/sensitivities/intolerances, methylation issues, and many other variables are what makes it too hard to tell everyone that one particular diet works for everyone...there are just too many variables for a one-size-fits-all approach.
More links you may find helpful:
http://gfmall.com/
http://gflinks.com/
(scroll all the way down to the bottom of these two websites for links to other helpful sites)