Google now does accept gambling advertisers, but the problem that brings is that,
advertisers who wanted to advertise on gambling related key words now can, so now it is very competitive, and because of this competition the price you will need to pay for your site to appear higher up the listings is a lot higher.
For example, if you want to buy something of "Ebay" and there is only 2 people bidding for that item, then the price will not increase by much. But if there are a lot of people bidding on that item, the the price will increase.
This is the nature of an auction based system, which both adwords and ebay operate on.
Also, to get you're site on the google page ranking you should aim for more niche keywords (or you can pay more).

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