Besides reading the manual and reference, the builder itself is quite informative. For instance, if you click ‘show documentation’ links on the upper right side of code boxes, it shows variables and objects that you can access, depending from the fields, properties, states that you set for the plugin elements and actions.
At the beginning, it really isn’t so much to fill in about you plugin, in the sense of plugin’s meta data. I got the impression from the reference guide that there’s a plenty of stuff to understand and decide before you start to write code, but it isn’t.
A lot of plugins have ‘see plugin code’ button on their ‘official’ plugin page, I learned a lot from those.
For instance, you can check if the user entered the reference to a thing or a list of things by this simple check:
if (properties.item && properties.item.listProperties) ...
if (properties.itemlist && properties.itemlist.length) ...
I suggest that you try various setups (header, initialization, update) with a simple input box or similar element, to see the behaviour. It takes a while to play with it, but you’d do it anyway - with or without tutorials …