Not all probiotics are good, many are a con.
Check out Liz Earls books and podcasts on the subject. I met her at an event and was incredibly impressed with her knowledge on the subject.
She takes and recommends Bio Kult so that's what I do. First thing in a morning on an empty stomach and nothing to eat or no hot drinks for an hour or so.
Also consider taking part in the British (well it's tagged onto the American really) Gut Project.
There are lots of forums on this fascinating subject and we know so much more about it now. Especially with the relationship between gut and brain health.
Don't go buying all these high sugar commercial drinks as a/ they are a con and b/ they do no good. My background is in marketing and I cringe when I walk round a supermarket or pharmacist and see just how much the general public are being ripped off with so called 'health foods'.
If you really want to get into to the subject and grow your own, consider reading Alberto Villodo's book 'Grow a new Body'.
He recommends a cleanse then a course of S. Bouloardii. You can buy it or make it yourself using a starter in soft fruits. It sounds a pain but I did it, it wasn't too arduous and you will have a strain for life if you keep it up.
His book also offers amazing insight into health and well-being.