The best SEO course that I can recommend is free. Just look up Brian Dean.
I'm not recommending his paid course, instead, I'm recommending his Youtube videos as well as his blog Backlinkle.
He is very thorough and you will get everything you need to get a running start.
At the end of the day, SEO is one of those disciplines that you only truly get good at, you only truly understand and master through doing.
People can throw you all sorts of instructions and possible theories but it's your implementation that will help you get over it.
You have to focus on what you're doing about specific issues within your niche and come up with custom solutions.
Courses can only give you a broad overview but when you're learning by doing that's when things start to fall into place.