First I'd suggest avoiding any foods that you may be intolerant or allergic to. Also, cut out caffeine.
Probiotic-rich foods may help (kimchi, sauerkraut, miso, etc.)
Reduce sugar consumption and choose lower glycemic fruits like apples, pears, berries, cherries, plums, citrus.
Eat plenty of protein and healthy fats (including omega-3s) from whole foods, not processed foods.
Try an anti-inflammatory diet: https://www.nutriliving.com/blog/top-10-anti-inflammatory-foods
Focus on stress reduction and getting proper sleep.