Fiddler

Are there any companies out there selling ads, ppc, traffic etc that work with their clients to help them improve conversions and get the most out of what they are buying?

If so get in touch with me as we're looking to buy a lot of traffic but only from suppliers who will help guide us through making the most of it (as they'll know what type of traffic their sending and hopefully which of our landing pages would be best). Of course we expect trial and error I just don't want to deal with a company that sells me traffic and doesn't say another word.