I would start with something simpler like a top down shooter.
But if you are set on doing a map game:
You need to know how to use:
global and local variables
Control flow (Events/subevents, else, and toggle invert)
How to use tiles sheets and tiledbackground.
System commands (pick all, for each)
After you have watched a couple tutorials on those topics you'really ready to start.
Character movement will be something like
on move event if character instance variable1 is greater than zero >
move character x pixels then subtract 1 from variable1
Else > out of moves
Subtract more if over rough terrain.
Character health and other statistics will probably be local variables as well.