I've been asked what plug-ins to use on a landing page and my answer is, "the same plug-ins you would use on any page." Use plug-ins that speed up how fast your site loads, plug-ins that enable people to share your site on social media and plug-ins that facilitate search engine optimization.
These are plug-ins I use on every page and post:
AddThis https://wordpress.org/plugins/addthis/installation/
does a lot of important stuff Use the AddThis suite of website tools which includes sharing, following, recommended content, and conversion tools to help you make your website smarter. With AddThis, you can see how your users are engaging with your content, provide a personalized experience for each user and encourage them to share, subscribe or follow.
Optimizes load speed. Jetpack plugin has numerous features that allow you to manage many different aspects of your WordPress site. One of the great features being offered is a notification toolbar that grants you with a full control over comments made on your posts. Commenters may choose to get notifications for new posts or for follow-up comments by mail.
Jetpack is built by the people behind WordPress.com and is designed to speed up your site, promote content, reach more users, and make WordPress sites instantly mobile ready.
Google Analytics
Gravity Formshttp://www.gravityforms.com/purchase-gravity-forms/
Lazy loading makes your site load faster and saves bandwidth. Uses jQuery and degrades gracefully for non-js users. Works with both images and iframes
W3 Total Cache improves the user experience of your site by increasing server performance, reducing the download times and providing transparent content delivery network (CDN) integration.
JetPack, Lazy Loading and W3Total Cache provide similar basic caching function, but have different features. Use which ever works best for you.
One thing I will say though, Jetpack is not reccomended by many here at WA for the reason that it is too many plugins in one and can cause serious problems.
As far as I understand Kyle has blocked the use of Jetpack from WA users, in the motive of helping people to not run into these issues.
All the best
Jason