You need to buy diamonds to progress further in game. At first it seems to be going just fine without using too many diamonds, and you might think that you can somehow managed on the diamonds you get for leveling up, but no. You end up having tons of gold and waste time in casino for a chance to get any diamonds, wasted about 30k going 100 wages and got diamonds once. Very enjoyable but waste of time if you don't want to spend money on the mobile game