The help pages in the Gnome and KDE desktops are a good start: press F1 and see what happens. You can browse the manual or info pages for interesting commands and try them out.
Rute User’s Tutorial and Exposition is an old guide available as a pdf (just Google), still useful for the command line tools. For more information, see Advanced Bash-Scripting Guide by Mendel Cooper, which is also on the internet.
You don't say how much programming you've done, so it's difficult to advise you. In Linux, very roughly speaking, major applications are in C and many housekeeping utilities in Python. Visual Basic is a Windows thing, but there are people who use Free Basic.
The secret is not watching videos, but doing things and seeing what happens. So long as you never change a configuration file with out making a backup, and keep a live CD distro handy in case you really mess up, nothing disasterous will happen .