The SEO certificates post includes a lot of learning resources as all the certificates require you to go through some training before you can take the exam. If you want a faster rout in a case where you applying a job that needs some SEO knowledge (not an SEO specialist job) you can find many online resources that cover the SEO fundamentals and give you a good jump start in your SEO knowledge
Search Engine Optimization starter guide (by Google) this should be the first document your read, it covers the basics of on-page and technical SEO
Google Quality Guidelines this is very important one to read especially if you are planning to be aggressive in your link building efforts
Google Quality Raters Guidelines Google uses quality raters (humans) to evaluate their search results so their engineers can improve them, what we learned about Google's logarithm throughout the years that it will always try to replicate human quality judgment, reading this document will give you an idea where is Google's algorithm going in the future
SEO Learning Center (by Moz) similar to Google's starter guide
Google Best Practice (mainly for ads) this is Google's best practice document for ads, quality guidelines for ads apply in most cases to SEO which makes this document worthy to read even for SEO specialists
Conferences to attend:
Going to conferences to learn SEO is not going to give you the best ROI however; going there to network and meet new people is the investment you should be looking for
Another benefit of going to those conferences is the status and the credibility it gives you with your clients (especially the big ones), major search engines like Google send speakers to many of those conferences so you will have a chance to hear from the horse's mouth, then you can communicate your SEO recommendations with your clients saying I heard Google saying this at SMX Advance for example.
