make it like a contest with different prize distribution. Lets say roll hunt for a specific number, players who roll it the most during the competition wins. This will make players keep on betting to hunt the number, unlike the previous roll hunt contest where players stop betting once they got the requirement.
If you join their telegram and twitter.
They make a lot giveaway everyday around 50-100$ for a few user, also they make a tournament Fight the Emperor every weeks on telegram group. That's why, I recommended all people to join their group or follow their social media to get some free balance from their giveaway or tournament.
Its all free.