When a publication solicits you to advertise with them and throws in “free design” as an added bonus, keep one thing in mind, their goal is to sell you the ad space. The designer’s primary goal is to create an ad you’ll approve. They aren’t going to consider how the ad will generate a response and how to track it. You’ll pay far more for the weekly ad space than you will for the initial design. This is not to say that you can’t get a good design from a publication that offers it for free, but you should know their motives for offering it. Very few publications care about your return on investment for the money you spend with them, they only care about selling the space.