Greetings, I've had a kinda despairful experience with the gold drops. I got worked up and bought 3 60 premium kegs this weekend for a total of 180 kegs, the results :
First 60 kegs = 5 golds. 1 premium 4 normal (from the first 4 picks). 1 vanilla geralt 1 vanilla Triss (meh).
Second 60 kegs = 8 golds. 5 premium, 3 normal. Got the first 2 premium golds from the first 2 kegs.
Third 60 kegs = 1 gold. 0 premium, 1 normal. Got extremely unlucky with this one, I expected the ratio to be at least 1 gold every 20 kegs so I got really sad with the results.
So in total from 180 kegs, I got 14 golds. That would be 1 gold every 15 kegs or so. I might be wrong but apart from the kegs I purchased, I haven't gotten a gold card for the last 20 kegs I opened. I guess it's completely random, either you are really lucky or really unlucky, there doesn't seem to be a fixed value every X kegs.