To my knowledge, that would be 7search.
The top eleven bids for the search term "online casino gambling" as of 30 seconds ago range from a high of (Advertiser's Cost-Per-Click: $5.13) to a low of (Advertiser's Cost-Per-Click: $4.99) but that's for usa traffic, and most feeds pay different for different countries.
"online casio" (Advertiser's Cost-Per-Click: $5.16)
casino (Advertiser's Cost-Per-Click: $5.07)
poker (Advertiser's Cost-Per-Click: $3.69)
online poker (Advertiser's Cost-Per-Click: $4.49)
Peakclick has some casino bids around $1.70 - $2.00 and accept more countries. Plus they have one click landers while 7search is 2 click landers. I know people inside both places and they are both pretty picky about traffic quality. They have to be to protect the advertisers.
I have accounts both places. 7search has more strong advertisers but conversions on those second pages being what they are for publishers, you will likely be about the same either way you go.
I'll pm you a peakclick referral link and if you have trouble at 7search contact me. Peakclick has by far the most extensive stats and robust reporting of anyone in the entire ppc industry. Once you create an account you can view bids too.
Hope it helps,
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