I've seen people get really extravagant with their designs and I can appreciate that. Terrariums can have multiple plants and succulents, trinkets, rocks, flowers, driftwood and even personal memorabilia. But in a cubicle, it's best to keep it simple.
Air plants are really the simplest, most inexpensive way to go. You can buy air plants at your local flower shop or nursery for under $10 depending on size. They can also be ordered through many different places online - I found a store on Etsy where you can buy a package of five air plants in varying sizes and colors.
There really is no limit to what you can do with your air plants. You can put them in any kind of container - glass jars, vases, bowls, candle holders etc. These are really great hanging vases from West Elm.
Ikea also has magnetic containers which make them very easy to display in a cubicle. They can attach to metal shelving units or storage/desk drawers.