Sadly, I also don't have a good ROI on AMS ads, but I sell most of my books that way each month, so it will be a while before I drop it.
That said, BookFunnel sales promos typically have high conversion rates from clicks to sales, particularly for discounted books--assuming you find a promo that's a good fit. Some promos offer the opportunity to promote multiple books at once. You can also run your own if you don't find one that looks like a good genre and thematic fit, but in that case, you have to plan further ahead--allow at least a month to build sign-ups. If you're signing up for someone else's you can typically wait until a day before it goes live.
Though you can in theory join as many as you want, since you need to share each one with your list, it's hard to do more than about two per newsletter. (More than that, and your followers tend not to produce much in the way of clicks and make you look as if you aren't sharing much. Most promo sponsors accept the fact that newbies might just be starting lists and social media, so they don't expect much in terms of shares from them. But people do look at share rates for authors who have been around for a long time and start setting minimums. That's why it's better not to try to work too many promos at once.
I've been talking about this in the career thread, but Substack may offer another area that promotes visibility. It's free to use, though the fact that most people on there are understandably looking for paid subscribers makes it a little more difficult to interact. Still, there is a certain amount of free interaction that you can use to get people interested in you. If you care what other people are doing and respond in substantive ways (with meaningful comments, for example), they will do the same for you, and you will gradually become more visible to people in other networks. Properly used, Substack can become a revenue stream. But there are some NYT bestselling authors on there who seem to be using it to broaden their base, so it must be worth something for that.
Basically, it's like writer-specific social media. Notes, a recent addition that runs on top of it and is like Twitter, but without the length limits, is a way to meet and interact with others. Following people on Notes is a real thing, it's free, and commenting on someone else's Note makes you visible to their whole network. If someone likes your Note, it also becomes visible to their network.
Of course, the idea is to convert as many people as possible to subscribers (free or paid). I'm free right now until I have more traction. Even so, subscriptions come slowly at first. But it is something to look at as a possibility. Subscribers get all your posts delivered to their inboxes. They can also view them on the site.
That's all I can think of off the top of my head.
