Best places/products to learn SEO for a semi newbie?

I'm fairly new to SEO. I'm familiar of what its capable of. And I feel comfortable enough to do it on my own sites at least in theory anyways.

But I'm wondering what are the basics of on page SEO, as well as the basics on page for Wordpress?

Whats the keyword percentage to be used in our articles, without being spammy? I think currently its 1%. I haven't written much and don't feel I'm a good writer, so the odds of creating a 2000 word piece of content probably isn't going to happen, not without filling it with needless filler or even at all for that matter.

Best WP SEO plugins for Wordpress that play well together?

Who are the leaders in SEO to follow?

Any recommended courses (including WSO's) that affordable for someone who hasn't made a dime online?

Who are the trust worth SEO people out there who truly are there to help and not just make a quick buck? Who's SEO advice should I avoid like the plague?

I'm more focused on on page than off, even though I know they are both important. I can get my hands on link building tools, but its the on page that eludes me.

I realize there's a lot when it comes to SEO, or so at seems anyways with on and off. I'm just not sure what I should, have need, etc. I'm curious what courses/products/plugins are out there. Just not sure the direction to go in to start seeing results.