There are many reported cures for rheumatoid arthritis, but it isn't clear which may work in your case, of if any can work at all.
For sure you have to have a clean diet (no sugars, no starches, no artificial components that can potentially create issues, no sodas, plenty of water - this is the easy part, in a way). Also enough vitamin D etc. plus exercise (indispensable to move fluids around).
After that are possible food allergies.