Top-10,000 Alexa site: $13/day from adbrite. Tips for generating more revenue please!

I run a fairly large vBulletin-based community site, averaging 500 to 1000 people online at any given moment, way over 140,000 pageviews/day and an alexa rank just under 9,000 (weekly stats are much higher, in the 6000s range) with most of the traffic coming from Japan, USA and Thailand (in that order, though it is an English-language community based site)
I only use adbrite (interstitials for guests only, no in-line ads, four banner zones) and my rates are falling. I am currently working on revenues in the region of $13/day
I have noticed that sites with similar or even less traffic are making more money, and I am curious what services would be recommended at this point.
I am by no means a veteran in this game, as this is my first real venture. I can cover server costs for two servers with the current revenue, but that’s about it.
Also, can anyone tell […]

See original post by chompy