First suggestion: ignore me because I am not a good example for how to promote your books. (I exist here and pretty much nowhere else - except, of course, actual resellers like Amazon, etc., and I do almost no self-promotion.)
Second suggestion: remember vydorscope? he used to be a regular here. He posted
My Journey To Self Published Success on his website. (
Apparently he has been so successful that he feels no longer feels the need to talk to us wannabes 
, Just kidding, Vincent!) That article makes good reading and matches up with what I've read elsewhere over the years: you need a good sized backlist of books (you have those), and you need a good marketing strategy to become visible - Vincent's article offers an excellent example of how that might be done.
Third suggestion: I still think
this advice from Hugh Howey is worth revisiting to remind yourself what self-publishing is about.
And, after reading those, you will probably work out that - IMO - the only 3rd party book promotion sites worth being on are those that sell your books - because that is where the majority your potential new readers are likely to find you. So get together a strategy, like that described by Vincent, to get yourself in front of readers on sites that sell your books for an extended period.
No strategy is a guarantee, but some combination of backlist, visibility and writing that "breakout" book that people finally notice is what you are striving to hit. I don't know of any 3rd party promotion site that will offer you anything close to what you might hope for by marketing new releases in an effective manner with resellers.