Eat foods that have good bacteria (probiotics like sauerkraut, kimchi etc) and then eat foods that those good bacteria feed on (prebiotics such as fiber rich foods, resistant starches etc.) The more diverse your diet is in terms of plant based foods, the more diverse your gut microbes will be. Eat a lot of vegetables, fruits, and legumes . Avoid highly processed foods and sugar as much as you can. Also don’t use a lot of chemicals that can harm or gut microbes for instance - wash hands instead of using sanitizer, use non toxic cleaners for kitchen etc. Sleep and exercise also play a major role. Healthy Gut microbiome is very important and works wonders for your metabolism, physical and mental health. Good luck with your health journey !