Basically you've made $6.41 in about a month off doing no thing, which isn't bad I'd ask for aleast 78$ (6.50 * 12), probablly more since it truly requires no work and could be built into a much more profitable site. The only expense would be renewing the domain name and anyone experienced with this sort of thing could optimize it and make it work well.
I would not sell it for less than a years revenue, no matter what you do. Gambling traffic is really worth alot, so it has more value than your average name. I would suggest going to domainstate.com and posting in the traffic domains section.