Where to begin with SEO?

Hi, I am from the UK and looking for an apprenticeship in digital marketing. While I have experience in most content creation areas I have 0 experience in SEO. I was wondering if anyone can suggest any good training resources to learn SEO from the ground up. I'm not looking to become an expert over night I just want to gain an understanding of how it works and the basics of how to implement it as I am hoping that this will give me an edge when applying for apprenticeships.

As I don't have a website to play with it's difficult to learn right now. I was actually wondering if there were any software or websites that allow you to practice coding for SEO as watching a 2-4 hour video about SEO implementation will just be boring and I doubt I will get anything from it. While I don't have a great deal of money right now, I am willing to spend money if I deem it's worth it.

Thanks all for taking the time!