I'm glad you're getting your hands dirty with WP, it's a great platform to work with, incredibly easy to install, configure and manage and it has (or so I was made to believe) the biggest community of people behind it.
About the YOAST plugin: this topic it's not the place to discuss it. You should start another topic, particularly related to that plugin if you want help/advice about it.
I've just started using YOAST plugin myself and I'm afraid I don't know enough about it to help you out with its settings. And there's also a thing of problems division, WP is WP, WP plugins are another story and most of the time the plugin creator has the answers, not the community.
Anyways, just to get this out of the way, setting the permalinks to /%postname%/ (would look like mysite.com/my-post/) is usually a good thing, please have a look here, here, here and here.
Don't take their word for everything, but do learn how seo works and why it's good to have human readable urls. It's a fantastic world of which you'll never get enough once you start to understand the whys and the hows.
Also, please have a look at the WP Codex explanations and usage:
(You can take these guys' words for what they say. :-) )