Just be patient and hopeful. Start with what you are comfortable with and slowly experiment with new features. It doesn't even have to be a game, it could be an demostration for yourself.
Yeah, I recommend this to. In the year that I've been using Construct I've amassed a huge folder full of little example .caps that I've made that are just simple experiments, mockups, tests, whatever. Just make a quick experiment whenever you get an idea. You might not even ever have a need to use it, but it's good practice.
I came over from MMF too, which I had been using about a year. MMF games can get bloated and sluggish pretty quickly, so when you're making larger games that you still want to run well you learn pretty quickly to streamline your code and simplify your events. So I guess one piece of advice I'd give is to always try to shrink your code if at all possible. Look for ways to squeeze two events into one, or if you have a bunch of similar events that do the same thing, try to find a way to get them to work in conjunction.
And above all, organize, organize, organize. Use groups and external event sheets to your advantage. And comment everything. You will thank yourself later. Even if nobody but you will ever see your events, make comments. I've made the mistake of making huge event sheets with no comments and, at the time, I had everything well organized in my head... but then I put the project away for a while. When I came back to it after a couple of weeks, I was totally lost.
Organization will also help when it comes to my previous piece of advice... when you get into the habit of organizing it naturally follows that your events will become more optimized. You not only see where things go, but how they fit. It's kind of like retraining your brain in a way. If you practice at being more logical, methodical, and deliberate in your coding it can only benefit you.
Of course, this doesn't apply just to Construct, but to all things. If you want to get better at Construct specifically, I'd suggest hanging out in Help and trying to answer as many questions as you can. That's what I did to teach myself. Half of the questions asked there I don't know the answers to before hand. I treat them like puzzles that need to be solved. I fire up Construct and run some tests and try to figure out what's going on. It's helped me a bunch.