How do I get better at building in minecraft?
1. Practice. If you're not already, consider using creative mode to allow for more time to be spent building and less time mining and worrying about enemies. Pick a well defined, small goal and work on it until you're happy with the result and then make a slightly bigger, more ambitious goal and do that.
2. Find inspiration. Working with no real inspiration can quickly lead to burnout or getting off topic. Collect images, solid models, and even save files from minecraft worlds of things you want to create.
3. Study the masters. Find out who is doing good work and view their work. If they're someone you can contact, ask questions!