I had acne, and always had tummy/digestion issues. I started with my diet. Anything that made me bloat was gone first.
Then I went on probiotics that can survive stomach acid.
I also pay attention to my saliva PH. It has been 7.2 for almost a year now, and my digestion is much better for it, because I have so much alkalinity.
But when it was 4.8, my stomach acid was low, which led to parasites, undigested food, and nutritional deficiencies.
I always make 1 new change at a time (one supplement at a time), and track it's progress.