Beginners of what? darktable? Photography? Image editing? RAW processing?
I would really shape that talk according to the users, whether they are new to editing or all already doing it one way or another.
With some basic knowledge presumes I would stick to the basics: get an image nice with a few clicks.
basic adjustments
shadows/highlights
crop
I would avoid filmic (many sliders, not much effect), monochrome (underwhelming, rather go color zones), and basically everything hard to understand.
Too many options in dt and lack of clear workflow that aims at 2 Minute edits.