When I started learning Construct I found it very useful to go through the templates and examples included with C2 to get an idea about how the basic behaviours and object types worked: you can access these by selecting File/New and then scrolling down the list.
The following features/objects will become invaluable as you move onto more complex projects so take time to study their usage:
Learn the difference between global, local and instance variables and their best use cases.
As dop2000 has already mentioned, read up on the different expressions - loads of seemingly tricky coding problems can be solved with just a single expression.
When tackling new material to learn, or if I run into a problem I approach it as follows: read the relevant manual entries, search tutorials, search the forums. In 90% of cases the solution is already out there; if that doesn't answer my question then I'll submit a post.
Beyond that, my advice would be to make lots of small games before moving onto anything big - in addition to getting you really comfortable with C2 this process will help you recognise the general systems common to many games, give you experience in formatting and simplifying your event sheets and establish a pipeline for development that will stand you in good stead when moving onto your magnum opus. It's also a lot more motivating to have a string of completed projects that others can play and provide feedback on.
Hope that helps, and all the best with your creations