You might be doing all the right things to generate leads -- landing pages, gated content, contests, and more. The problem might be that the design or copy itself isn't driving the engagement you need. A/B test (also known as "split test") different aspects of your list-building campaigns with different versions of the same content. This includes the call-to-action text, the color of the gated offer, the time of day you're posting to social media, and even where on your website these signup forms are placed. Sometimes a small change can drive hundreds more conversions.
There are tons of websites and publishers out there that cater to your audience -- and larger portions of it. Guest blogging for these websites helps you expand your contact list to this audience. When creating content as a guest blogger for another website, include a call-to-action, as well as a link in you author byline, for readers to subscribe to your site's blog or email newsletter.
At the start of my online career i used to think that list building has no benefits but after doing some research on the topic and starting with the link building thing i came to knew it’s importance. It’s really necessary for website and blog owners to build lists or they’ll just let their selves down because list building is the game changer when Search Engines and Social Media doesn’t work for you.
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.