The lowest cost ballast is a small choke designed and sold with the tube.
Electronic ballasts are designed for particular tubes and difficult to make as components are not marked.
Best buy a tube encapsulated with a ballast. You can build a RF oscillator for battery operation but you must experiment.
That should win an award for the most complicated way to draw a bridge rectifier.
It runs the tube on DC and without heater current. Expect a short tube life and unreliable starting. The available output current is almost entirely set by the 2.2uF capacitor, adjust it's value so XC = the value needed for your tube current.