One thing that really helped me was when i started using ruby on rails. This framework introduced me to the idea of scaffolding. The basic idea is to just generate large sections of a web application. So you can generate a database table called fish, and rails will generate a delete, Post New etc to change these items using html or in a API.
So I would advice to just start making a API with a tool you are familiar with or learn a new one if you have enough time and just start experimenting.