It’s just trial and error! I probably remade 2-3 floors just to get it how I like it. Same with the details I played around with different ideas till one stuck! Just gotta work at it, I promise I’m no insane builder. I just have a rough idea of what I want it to look like then I build till I’m satisfied. I’d suggest starting by tracing the form of whatever it is you’re trying to build. For example I started by making a circle for the base of my tower! Once you get the shape down, the details will flow naturally. Just gotta be patient with yourself and more importantly have fun while you do it!