How can I go about changing my diet?

Me

I have been dealing with pain and possible autoimmune symptoms. I’m allergic to Advil and Motrin so I can’t take anti inflammatories. I figured the best thing to do would be to change my diet so I decided to take gluten and dairy out. Plus I want to start drinking more water. I figured that gluten would be easiest to start with as I already will eat some gluten free foods whereas I eat dairy on a regular basis. How can I go about gradually changing things in order to help with the pain and other symptoms?