Unsweetened plain yogurt with active cultures is good. Plain, unsweetened Kefir is better (not as tasty in my opinion). 1 Billion Acidophilus is good (I take 10 Billion), but it's best to get refrigerated kind. Some people differ with that opinion, but that's what I believe just based on a lot of reading of different opinions on the matter.
I'm not on abx, but because of my messed up gut I take three different brands of probiotics with various strains and mix them all up. I take them with meals and prior to going to bed. Hasn't cleared up all my stomach problems, but it's helped considerably.
Sometimes you just need to try to find what works best for you. But, for sure, yogurt is good as long as it isn't laden with sugar and it has live cultures in it. My wife eats yogurt (Stonyfield brand because it's organic) three times a day--she really likes it!