I can’t comment on which kefir grains to get because I have not used any (yet.)
If you search for kefir, you’ll find some links in the forum on recommended brands.
I just purchased water kefir grains (http://www.savvyteasandherbs.com/products/Water-Kefir-Grains-Japanese.html) and they are still brewing. Won’t be done for another 2 to 3 days. I never liked milk/yoghurt and these actually sounded tasty with lots of probiotics. I’ll let you know in a couple of days if I like them.