Sorry to hear that. Most chronic gastritis is caused by a bacterial infection in the stomach, so eliminating these sugary foods may inhibit the growth of the bacteria as well. Yes, a keto type diet coincides nicely with the candida diet, however you may find that high fatty meats like bacon and sausage irritate your stomach. Perhaps keep away from those types of meats right off the bat and stick to the leaner, easier to digest proteins like chicken, lentils, light fish (tuna, cod, tilapia, salmon). But you are welcome to incorporate red meat whenever you feel like testing what your body can handle! You know your body best or at least will know it better once you are on a diet regiment like this. Avoiding the sugar, high acid-forming carbs, fruit should help against the gastritis even if it is not bacteria related since these types of foods cause inflammation and irritate the stomach lining. Also, if you aren't already taking one, I would recommend a daily probiotic capsule to help your gut bacteria fight off the H. Pylori (bad bacteria). Plus, probiotics are good against candida as well.

Here's a handy list of food that helps against candida. It just so happens that these types of foods help eliminate stomach inflammation as well: https://www.thecandidadiet.com/foodstoeat.htm

If you decide to do this diet, please let me know how it works out for you! Good luck and God Bless!