What are different ways to treat gilbert's disease?

Don't treat it. As a lab doctor / pathologist, i'm always telling folks to treat the person, not the lab values. Phenobarbital will lower the bilirubin level and make you chronically tired and slow. Call it "gilbert's non-disease." only a few people ever have trouble with it.
Nothing. Gilbert's is usually an assymptomatc disease that's incidentally picked up with routine blood work. We usually don't treat it.