Longterm average is 70 jewels a day if you never miss a day. IIRC the login bonus adds up to 240 jewels over 12 days, for an average of 20 jewels/day. Of course, since it's in a 12 day cycle, you don't exactly get a roll every 4-5 days. But if you're planning for months down the road, the 70 jewels/day average works as a baseline estimate before taking event gains into consideration.

And then on the other end of the spectrum, there's Aigis. A premium roll takes 5 crystals. You are handed a crystal on the 5th, 10th, 15th, 20th, and 25th day you login for each calendar month. No, not the 30th; gotta be fair to February. You're basically reliant on event gains here, although the longterm average of event crystals is below 1/day.