Thanks for comment Fred, these tutorials are looking promising.
In general I would recommend Laracasts and Laravel documentation itself. It doesn't matter if Laracasts videos are for Laravel 5.4, once you fully understand how the things are working, you'll see that the differences are small and that you can easily understand Laravel 5.6.
If you have trouble with the laravelcollective/html package used for rendering some HTML elements (including form tags) in Vanguard, check their documentation on https://laravelcollective.com/docs/5.4/html
You will see that they have the docs for Laravel 5.4, but it works the same for the latest Laravel version.