I have an idea for a website that will attract many visitors.
If you are sure that you will be attracting many visitors then you will make a good enough money with good ads itself and make sure that you do not fill up all the space with advertisement so that it annoys visitors, it all depends upon what kind of idea you are coming up with,the more the visitors the more money you are going to make.
Yes, you are right, the site should be very attractive to visitors. A lot of advertising will not attract people. It is necessary that the site was interesting to a large number of people due to its relevance