How many sprints do I need?

The number of sprints you need depends on your end goal. If you want to experiment with a new method of marketing, you may need only one or two, if you are looking for a more aggressive campaign for your general marketing to boost weaknesses in your current strategy it may be four or five. Gauge your success after the first sprint, and use it as a metric to determine how many sprints you may need. If your success continues, and you keep gaining leads, consider where your weaknesses are and focus the next sprint on the weak points.