The Self Publishing Review site has produced an exhaustive list of resources for promoting your ebooks.
The richness of the tools are sorted as follows:
Writing and editing – tools, which can help you better write and edit your book
Design – how to easily prepare a cover of a book; it’s actually easier than you think
Formats and conversion – tools to convert and prepare books in desired file formats
Publishing – a list of the most popular self-publishing platforms
Online presence – what you need to effectively promote and sell your books
Reader engagement – tools to engage your readers in your books and writing
Analytics – analyze effectiveness of your online activity
Maybe spend an hour on each category and prioritize your top three tools. Once you focus on those, you can return to the list to teach yourself more about the other items.