>>6705520Taking existing sets and modifying them is a good way to start.
Like taking a modular building and adding floors to it or combining two modulars in to one building.
Another great way to get started is to try adding power functions to a set that doesn't have them or isn't intended to work with power functions.
I recently took out my old 4708 Hogwarts Express. The set is intended to work with a 9V train motor (old style), but making it compatible with modern power functions was a real challenge. I added a tender car to hide the battery box and it also has lights at the front and in the passenger car. I took some inspiration from later models and ordered some extra parts on bricklink to finish it up, but overall it's my own creation and I'm really happy with it.
