You can make more selling directly (or selling to someone like GSM), but frankly, you don't have enough volume (yet) to be of any interest to most media buyers.
I'd suggest something like
AdSpyGlass(ref link) -
https://www.adspyglass.com (non ref link) until you're able to attract direct buyers.
I use it for roughly 1m daily imps on my main tube and so far so good(understatement, really). AFAIK, there's a 1 month free trial still.