Start with Tutorials.
Don't read them. Build the example games step buy step.
Build this first
Construct comes packed with examples. New project and scroll down to see all the examples etc.
And the most valuable resource - The Manual This has everything you need to know.
And search the forums - so much info here.
And of course, the most important. You cannot learn code/programs etc without coding/working with programs. So in a week you will be pretty effecient in construct 2. And spend 1000 hours and you will be a pro.
Game maker will take you a lot longer as the learning curve is steeper. I come from game maker originally.