Btw, is it possible to see my total wagered amount? Asking because what I can see in my personal stats regarding my multiply btc rolls is only this:
The reason that isn't displayed is that it wasn't tracked from the beginning of the site so we don't have fully accurate numbers. We're probably going to add it soon as that only effects accounts that signed up in the first couple of years.
But as far as I understand there's a wagering requirement for increasing your FREE BTC rewards, right?
That's right. It is a ratio of free winnings to wagered on dice, jackpots and lottery tickets bought.