What do you find more profitable? Picking a top website and selecting an offer for that audience or, on the contrary, choosing an offer first and adding relevant targets ?
You can do both, if you have an offer you wanna promote you can go and find the demographics for it and then the targets.
In the other way, i also grab lists of big volumes targets and go from there, study the demographic, then find an offer than can work.
Both can be effective.
Mehdi