How to Get Started on RDL reporting on NAV 2016

We're moving from NAV 2009 classic to NAV 2016 and I'm trying to get my head around RDL reporting.

Where should I start, which ressources are available online ?

Does the learning curve is pretty steep ?

Seems like you know a lot of VB Script pattern for the RDL layout, where can I find more info about those expressions and what they do.

Any productivity tips and advises on RDL reporting is welcome