Now that there are thousands of self published books added to Amazon every single day, the only way you're going to get your work seen is to advertise. If you're not active on SM, that means ads. Both Facebook and Amazon work, the latter more if you're in KDP Select.

 

Got my first reader when i published first paperback book at Authorhouse. Did not use their promotional services because they seemed too expensive. After publishing one more paperback there, started publishing at Amazon, then Smashwords, which has since merged with D2D.
Only ad service used has been Booksniffer, which seemed to give good results. Looked like it folded, my last contact with one of their people spoke of a reboot, which never materialized.
Main promotion has been offering first book in four different series as free. But it is not possible to determine whether readers of first free books in series are the same readers who purchased later books in the series.
OP: thank you for starting this thread. Am looking forward to reading what other authors have experienced.