Increasing PR is the easy part. Actually being found in the search engines for even mildly competitive gambling keywords is all about the number and quality of links you can get pointing back to you. If you are only looking for exchanges that result in traffic, then there are a few sites out there. If you are planning on rising up in the SERPs, you will need a ton of links.
Since Dom is being used as an example (sorry Dom), I will point to the fact that her site has 43,345 backlinks, so it would be expected that her site is ranking well for the terms being targeted. Our site has 5,597 backlinks and is still being ignored by Google (thanks Yahoo though).
It should also be mentioned that reciprocal links is by no means the only way to gain backlinks. Creating a ton of content, writing articles, participating in forums such as this all gains you a link that counts.