How long is the estimated Construct learning curve to achieve intermediate, advanced, etc. levels? Is there a preferred way for gaining experience, ie game types to create in a given order, etc? (I know about the tutorilas, but beyond that.)
I've been at this for going on three years now, and I would say I'm solidly at "intermediate" level. On the other hand, users like Quazi reached "advanced" in a really short time. It all depends on your ability and how much work you want to put in.
As for gaining XP to level up your Construct mojo, it's recommended that you start with Ghost Shooter and work up from there. There are a lot of different tutorials available, just pick ones that interest you and follow along.