I would start with simple navigation commands:
ls- list files/directories
cd- change directories
Then move on to moving and changing files
cp- copy files
mv- move files/rename
cat- read files
mkdir- make directories
rm- remove files and directories
man <command> - this will tell you how to use the commands and give you different switches for each command.
I would only try these in your home directory first until you are comfortable with the commands.