try to watch out what foods make it worse. I don't think there is any specific diet. For example many people swear by low carb diets (in terms of doing good things to their mood), but for me... if i don't get enough carbs, I feel starved, I feel like going crazy. With time I realized I am sensitive to some additives in food... I survive them in smaller amounts, but long term... it makes me crazy.

Look up mood foods. Legumen are the main mood food for mood disorders. Fish are another.

Another thing I found extremely useful is Bach essences.

This link sums up the ones that are useful for bipolar Bach Flower Remedies | Emotional Wellness but there is 38 remedies total, which can be combined (max 7 at times) into customized remedy.