Hi,

if you need to uncover new interests, you might find Facebook Graph Search useful (you need to have your Facebook language set as English US before anything else).

Start typing this phrase into your Facebook search bar: "Pages liked by people who like XYZ" - this will open a list of the most common pages of people that also like XYZ.

You can get even more granular:
- Pages liked by people who live in United States and who like NBA
- Pages liked by people who live in United States and who like NBA and Houston Rockets
- Interests liked by people who live in United States and who like Basketball

As you said, trying out lookalikes based on your custom audience, website custom audiences, or conversion pixels could be another way.

Also, one additional way to bring your CPA down would be to remarket to everyone who have already visited your website by using Perfect Audience or Facebook website custom audiences.

Finally, you should have some strategies implemented for overcoming ad fatigue. Instead of running a campaign continuously for a very long time, use the newly added scheduling feature to spread it out: have it active for 1-2 days, then add 2-3 days off. Also, upload numerous different visuals for the same campaign and set up ad rotation, so that every 2-3 days a different ad is shown to the audience.

I hope this will help you improve your campaigns, and if you wanted to discuss it further, feel free to let me know!

Cheers,
Adomas

Some great suggestions by Adomas. Here are few more you can try -

- target people who like brands (which you sell on your site)
- target people who like 5-10 competitor's sites (for each product category)
- find pages/interests liked by people who like your page and get ideas from there
- expand your lookalike audience beyond top 1%

Above should help you expand your reach. Now to increase conversions, you must do re-targeting for those who visit the site and you must keep expanding the lookalike audience based on your "buyers" list.

If you need more help in setting up or scaling up huge campaigns, let me know.

First of all, always find out what your competition is doing. Then use the scientific advertising approach (Claude Hopkins), test, test, test. One way of testing is to make your ads more interactive.
Don't stop taking massive action.
Best of Luck,
Michael T. Irvin
michaelirvin.net
My books are available exclusively through Amazon Books. Check out my book "Copywriting Blackbook of Secrets"
Copywriting, Startups, Internet Entrepreneur, Online Marketing, Making Money