There’s some really solid advice here (and some not so solid advice *cough* Moz *cough*). I learned SEO through emulating case studies and just trying to get sites to rank in order to turn a profit. Most of my experience came from sites like [blackhatworld.com](https://blackhatworld.com) and through access to people at google whom I had direct access to due to the quantity of clients’ ad spend with Google. That type of access is virtually impossible today.
A lot of quality auditing software/services out there. I have accounts with AHrefs, SEO PowerSuite, CORA, and others. My audits typically has data from all of them. Pulling audits from each and using what you need is what I would recommend.
Several here appear to be offering free audits. Go ahead and grab them and use them to help you learn the type of content and analytics that are typically in audits. I’m a huge proponent of CORA because it has hands down THE best auditing available. CORA gets data from sites that rank top 10 in Google for your keyword phrases and gives you a detailed list of what you need to do and which ranking factors to focus on in order to get your website in the top 10 in Google too. There are a number of reputable SEO sites out there that will also offer you free auditing reports. Reach out to them and request audits too.