1. Aiming at becoming a Selenium automation expert
This goal is so high that you will probably fail.
You should replace it with something more achievable like “i want to get a test automation job in 1 year”.
2. Selenium WebDriver certifications
Selenium WebDriver certifications are scams. Even if they would be good, they wont help you getting hired. When studying for a certification, you study for the exam that you will take and not for the subject.
Passing an exam is a very poor way of measuring your programming skills.
I met people who passed with 90% grades TOEFL (test of english as a foreign language) and TWE (test of written english) but speak and write very bad english.
3. Jumping into writing Selenium WebDriver tests before learning a programming language
Test automation with Selenium WebDriver is basically programming.
Without knowing a programming language well, you will always have big obstacles in writing automation code. Selenium WebDriver is just a library that can be used through multiple languages.
Jumping to Selenium tests with no programming is similar with trying to cook lasagna with no cooking skills.
Shortcuts never work. There are no shortcuts to math, to learning french, to getting fit, to anything. You have to put the effort in and follow a process that takes time.
4. Looking for the best selenium book or online course
There is no such thing. You will find though many great books and online courses.
The best book for Selenium should include everything about Selenium, everything about the programming language (lets say Java), everything about an IDE (example: Eclipse), everything about unit testing, maven, code design, code refactoring, maven, etc.
Do you really think that it exists?
It does not.
To learn test automation with Selenium, you need to use a multitude of resources, books, blogs, youtube videos, online courses, webinars, etc.
Because the amount of information needed for an automation job is very high.
5. Learning by yourself
If you attempt learning by yourself, chances are high that you wont make it.
Find other people with the same goal, take instructor-led courses, find developers willing to help you, go to meetups, anything but being by yourself.
6. Selenium IDE
Record and play is not test automation