Well gambling is not the best way to multiply or to grow your bitcoin fast because gambling is for fun and you will lose your bitcoin fast..
I think the best way to grow your bitcoin is to buy and sell like but cheap account and sell it expensive.
You may also try trading with bitcoin into fiat and fiat to bitcoin. If the price of bitcoin is very cheap or cheap buy it and if the price is going high or expensive sell it.
I just want to remind you that investment or cloudmining site is not the best choice to grow your bitcoin because it will turn into scam in few days...