If you business is already existing and you want to gain traffic, this site is the best place to seek for advertisement.
One of the popular method is the "signature campaign", we have good campaign managers here and in relation to rates, you can find that information in this thread
Overview of Bitcointalk Signature-Ad Campaigns.List are updated, you can use it to analyze on how successful running a signature campaign, so far there are still active campaigns and we have
a lot of campaigns in the list that are running for over a year already, so it's not only during the starting period, it's also to maintain advertising and they will not be doing that if they are not getting a good return from signature campaign advertising.