www.insidecf.blogspot.com I just posted last night about my journey with supplements.
I recommend looking into probiotics. I use the accuflora brand b/c its cheaper, wider variety in cultures, and I double it.
I also recommend Vit C b/c it boosts the immunesystem. My non-cf daughter gets 500mgs a day.
Also garlic is a natural antibiotic. You can get it in supplement form - but You could buy the real thing, blend it, and give it in a dropper (Id say this is the most effective way).
Also look into vit D, fish oil -anti inflammatory... hum O and maybe Fizzy-NAC -but you have to order it from Canada.