Glad that I found someone with similar background as me here..
When the first time I learned SharePoint about, I thought of it as a platform rather than a product. So you could build custom content, pages, etc there.
Maybe the first part is to learn about Web Part (built in WebPart in SharePoint and custom web parts). One of great example with downloadable code could be found here.
When I started to build custom webpart on SharePoint (my first webpart was a simple table showing 10 recent documents from a doc lib), basically I just thought the lists and libraries as database tables (maybe because most of my projects are playing with displaying list and library items in custom layouts and formats), so basically you could do query (CAML Query, I found a great tutorial here).
After you are familiar enough with webparts, I think you will be started to be accustomed to the development steps, and maybe you will try another thing such as develop a Custom Application Page for example.
After starting development by playing with SharePoint webparts, list items and libraries, the next step I learned was the Event Receiver, which is basically code that will be triggered after a certain event (another great reference here).
The next step I learned was the workflow. It is not very capable as other BPM softwares, but it is pretty good and straightforward for simple tasks (I had only used SharePoint Designer workflow though). There is a good tutorial for SharePoint 2013 workflow here. Maybe after this part, it is good to explore more on Custom (Visual Studio) Workflow.
And that's all I could share about the SharePoint Development on my early days (of course maybe it is not the best practice, and of course I am still a long long way from mastering SharePoint Development), but in my case, it is pretty effective way to learn and develop custom solution based on my client's requirement on the early stage as a SharePoint Developer / Consultant / Whatever.