What is the most efficient way to promote/advertise/market eBooks?

These are my eBooks:
Athletic Body in 90 Days with Weights- goo.gl/UAlb6t
Athletic Body in 90 Days with Calisthenics- goo.gl/aG6939
From 0 to 30 Pull Ups- goo.gl/yqriuW

[SteveHawk]

Here's a link to a spreadsheet of the sites I use for promotion of my e-books:

https://docs.google.com/spreadsheet/ccc ... ring#gid=0

Some are free, others are paid. BookBub is the best IMO, but your books have to meet specific criteria for number of reviews, ratings, etc.