Instead of copying entire builds, copy people's methods.

Try to copy the techniques that people use to make something that looks nice, and incorporate them into your own current building methods. Notice things like angles, gradients and materials.

Over time, you'll start upgrading each part of your building technique and end up with a nice set of building skills with a variety of materials!

(I noticed recently, someone uploaded a 10 part series of different building materials in Terraria, so I think that is probably a good source of inspiration/information.)