This was originally a reply to a post about the effect of diet, but I wanted to send it to all, because I find good news stories can be really helpful and inspiring.
When my daughter was diagnosed with Lupus 3 years ago (age 17) we did loads of research and she decided to cut out gluten as there are many studies which suggest links between gluten and autoimmune issues (though she had no signs of intolerance). That was closely followed by cutting out dairy and refined sugar for the same reason (lots of anti-inflammatory books highlight gluten, dairy and refined sugar as the 3 primary food triggers of inflammation, in that order I think, although everyone is different).
About 9 months ago she decided to go vegan as well (for ethical reasons), so fish/meat/eggs etc. now also gone. She still finds being gluten free and vegan easy when she's cooking (she's at uni in self-catering accommodation) but eating out is obviously harder. Actually, not too hard in the UK now - loads of vegan/gluten free places in cities - but travelling is a challenge. Went to western Ireland (Cork area) a couple of years ago and that was brilliant. Lots of places getting better now.
Her health improved ENORMOUSLY which she largely puts down to her lifestyle choices, including her diet, exercise, yoga, learning to manage stress levels (huge trigger for her), etc. Her medication is down to one Hydroxycholoriquine per day and has been for some time.
Back in January, her blood tests showed her bloods had come down to NORMAL!!! which the lovely lupus specialist in Birmingham, Professor Gordon, said she had rarely, if ever, encountered before!
Luckily she likes cooking so she makes loads of delicious food, which is not hard when cooking from scratch (LOADS of veg, spuds, non-gluten grains, lentils, beans, fruit, herbs, spices, etc.) but would be much harder if you're used to fast foods and instant meals. Luckily she didn't eat those anyway so the switch wasn't so hard and the benefits have been really worth it.
In terms of buying special food, although most gluten free bread is not great, she has found a brilliant one which is also vegan and widely available in UK/Europe. The brand is Schar and they do loads of different varieties including loaves, ciabatta rolls, wraps, etc. It's actually really good. I sometimes eat it even though I can eat normal bread. In the UK, large branches of Morrisons (mostly in the North) have the best range of Shar products, but Tesco, Co op, Sainsburys etc. also stock it. For people who like biscuits/cakes you're probably better making your own flapjacks, chocolate mousse (amazing GF/vegan versions online) etc., rather than trying mass-produced GF stuff - much nicer and healthier. Edinburgh has several cafes that do vegan/GF cakes, so I'm sure other big cities have too (sadly not so easy here in Rutland).
Incidentally, since becoming vegan as well as GF/Dairy free, her health has improved even further so most of the time she feels 100% back to pre-lupus health, apart from fairly short-lived flare-ups triggered by sunshine (occasional slip-ups on the factor 50) or stress.
So really worth trying diet/lifestyle changes. My mother-in-law is always trying to make her old favourite staple recipes with substitues so that my daughter can eat them, which doesn't really work that well, so one final tip - don't try making your old favourites with complicated substitutes, but experiment with new recipes which are GF/DF/V anyway. You can find loads online.