I'd encourage you to spend some time surfing various suppliers' websites for ideas and to familiarize yourself with some of the pre-fabricated options on the market. Once you have a good idea of what's available and at what price point you'll be in a good position to start thinking about how to execute your vision. Fabricating your own elements can be a lot of fun, but also a bit challenging when you're just getting started.
I find it very helpful to sketch out my vision on paper. I tend to layer my sketches, starting with general positioning of elements, then going back and adding specifics such as bulb type, color, and electrical circuit until I have a robust blueprint from which I can work when it comes time to install.
With regard to electricity, it is important to match the requirements of your vision with the capacity of your location; if you want to run a 100 amp display off a single 20 amp (standard household) circuit, you'll be setting yourself up for disappointment. Don't hesitate to consult with an electrician if you have questions/concerns about working with electricity.
Electrical capacity may also influence your choice of elements/materials. For example, LED bulbs use substantially less power than incandescent bulbs, which means you came run more of them (i.e. have a bigger display) per amp.