The most challenging step when building a plasma globe is the evacuation of a glass container on the cheap -- vacuum pumps can be pricey. However, a good quality glass jar w/a narrow neck, a rubber sink stopper, a threaded bolt, a suitable high voltage power source (such as a Tesla Coil), tap water, some hardware and epoxy as well as access to a freezer are what you will need to assemble this simple project. If you can boil water, this project will be will be a breeze. :>D
Of course, use common sense and always keep safety in mind while operating the globe. This project involves electricity and water! If you accidentally connect with the high voltage circuit, the resulting shock can really ruin your weekend plans.
For Further Info
Step 1: Prepare Stopper & Assemble Discharge Electrode
Drill or punch a hole in the stopper's center just large enough to accept a threaded bolt. Secure the bolt in place w/a washer and nut on each side as shown. The bolt, which will be the discharge electrode, should be long enough so the head is positioned near the center of the flask.