busybox --help
this will get you a list of commands the busybox can do
busybox --help
this will tell you more about the command
Most commands are similar to the normal linux commands so linux tutorials are still relevant.
symlinks: ln -s <original> <link>
remove recursive and forced, the waay too dangerous for newbies to use: rm -rf <file/directory>
copy a file: cp <original> <new>
move or rename a file: mv <original> <new>
list all files and directories in long format: ls -al
filesystem stats: df -k
change directory: cd
make directory: mkdir
remove directory: rmdir
switch user using their profile: su - <user>
I suggest learning vi if you get comfortable with commandline