You may try bitcoincasino.fm, they give 30mbtc on sign up with 50x rollover requirement.
P.S : I'm not really sure if it is a legit casino or not, but at least you can try their site for free and without any risks
+1, I tried there but I busted when I played 6X rollover, 50X rollover is difficult to achieve, but it is risk free.
And satoshibet offers 10mbtc weekly(nowadays it is 2 week per code) with 50X rollover, what you need to do is subscribe them, can't find the link now, you should try by yourself.
to improve Wager I suggest you to play roulette. I always do that. proven several times I managed to make a withdrawal. but I also still ever felt run out of funds due to Wager haha