What would be the best way to market this website?

A couple of friends and I run a new (only about a month old, not counting downtime) Pokémon adoptables website that is starting to get a good amount of traffic but really isn't making much through Adsense. On the first week it was launched, it was making 'ok' revenue (or that we thought was ok for the traffic) once it started hitting 400k impressions a day, and we thought it would only go up as the impressions and clicks went up, but that sure didn't happen. We now obtain between 800k and 1m+ impressions a day but aren't making near what it happened to generate during that first week. We didn't create the site to get rich or anything, but we would like to finally have a revenue stream from our websites that can actually pay for the server without having to pay out of pocket. Our traffic will only increase in the future too as we get tons of new members a day. It's Pokémon and an adoptables website; it just screams traffic.

Anyways, the website is http://gpxplus.net

It's a sub-site of http://www.gtsplus.net/ which we would also like to find a way to market. I do not believe we can use adsense on GTSPlus due to when we first opened the website, we were letting someone else use their account on the site since we did not have one of our own, and their account was banned for foul play, and we read that once an account is banned, the sites that used the account pretty much get blacklisted. We tried AdBrite on GTSPlus but that really did nothing at all and no advertisers ever tried to purchase space.

Basically looking for some suggestions on what the best route would be for selling advertising on the sites. Thanks for any help anyone can provide.