I heard of people getting great benefit from it, as you say, there are many different qualities out there, depending on your location, I know of many places that are basically a front, jumping on the CBD bandwagon to make a quick buck. There even companies out there that a truly just a scam. Your best bet in my opinion is get some cbd flower, its less economical, but I think it's a safer option with a higher success rate of it actually working.
There are some who state CBD only works in conjunction with thc. I've never tried a CBD only product, Idone my research though, and personally, I just smoke weed, would rather get high than medicated to be honest at the moment.
Tldr : oils and tinctures are a crap shoot. Try CBD flower.