I kinda like the idea of getting some free coins for posting.
I don't like the idea of promoting gambling sites or mining gear/contracts.
Is there anything else that pays?
Gambling and mining contracts are among the few kinds of websites that can afford to get signature campaigns.
My suggestion is to try out all the gambling sites and find one which you personally use and believe in , then you can make your signature campaign well.
And last but not least , remember that you are selling your space for money and should not expect too much.