The scheme is simple: the more -- the better. Though, you should not be put back by the false assumption of your traffic flow being too weak -- give it a try and see how it goes.
Usually it requires about 10k unique visitors per month to start with. Concrete answer on your question hugely depends on your audience structure and number of variations.
Usually it requires about 10k unique visitors per month to start with. Concrete answer on your question hugely depends on your audience structure and number of variations.