Lesson 1: It is IBM i that you are working on i Series was superseded many, many years ago <grin>
Probably the best place if you want monitored/mentored learning is Jim Buck's
https://impowertechnologies.com.
Jim has a great reputation and a long history of teaching real world RPG and IBM i.
There are a number of videos on YouTube (including a few that sadly insist on calling the system an AS/400) for RPG stuff look for folks like Liam Allen.
The other option training wise would be The 400 School
https://www.400school.com but I suspect their offerings are more formalized and more expensive.
If price is a limiting factor the Jim Buck's books would be a low cost option - they are the ones used by most of the schools that teach IBM i. Make sure to get the latest version of this one
https://www.mc-store.com/collections/to ... th-edition it is also available from Amazon but the publisher is offering an extra 20% off list price (code is Top-10-Apr-22) - also by Jim is Mastering IBM i
https://www.mc-store.com/products/mastering-ibm-i which is also widely used in schools.
This list is wonderful for Scott's open source tools but for general purpose help on IBM i midrange.com and code400.com are better options.
Good luck!