I can only speak as to what personally works for me, and as my best ad site isn't even known in NY, that won't help you at all.
I get more hits from TER than any other site. So definitely take advantage of the Ad Boards weekly, but also try to post on your Regional Board from time to time. It definitely helped me when I was new here!
P411 has been better for me lately, but sometimes I don't get anything from there for weeks. As to the upgrades, well... it's really a YMMV thing.
Eros can be really good for some ladies, but others barely break even on their ad investment. For me, it just didn't work because very few guys who contacted me from that ad did not meet my screening requirements. But that's for my local ad.
For traveling/visiting ads, Eros was very good for me!
And when things are slow, I'll put up a local ad there and it'll help at first, but it seems like a listing goes "stale" pretty quickly on that site.
You might want to try Slixa, Sugarnights, MyProviderGuide, and CityVibe.
Hope that helps