Include social sharing buttons and an "Email to a Friend" button in your marketing emails. That way, you'll gain access to their friends, colleagues, and networks and expand your contact list. At the bottom of your emails, include a "Subscribe" CTA as a simple text-based link so that the people receiving the forwarded emails can easily opt-in, too.
Your list should be your total collection of contacts, so you should only need one overall list. If you still choose to create multiple lists, be aware that lists are independent of each other. They don’t share data or contact information. For example, if [email protected] is in two of your lists, we count that as two people. It’s almost always best to have a single list, and use our list organization tools to separate and manage contacts.
Some ad platforms will ask more of your landing pages than others, when running ads. For example, AdWords is much stricter, when compared to Facebook. AdWords typically requires that you do not have a ‘thin,’ site that is designed solely to collect leads. Because of this it might be a good idea to focus on using Facebook or Twitter, to begin with.