I love plants, I think every room can be improved by some living color, but I killed the first few plants I ever had. Basically I over-loved them with too much water, bad planting, and not looking into the basic requirements for their survival.
One of my worst plant murders was the planting of succulents in a "cutesy" terrarium, this is a popular look right now, but it goes against the natural environment these plants thrive in. Succulents and cacti prefer low-humidity, more arid conditions, to be deeply watered in the growing season, but left alone when dormant, the opposite of a terrarium.
So after finding a large glass jar with cork lid I started looking for moisture loving, medium light plants.
I used white stones on the bottom and then a clean dust sheet to keep the soil from falling through.
I added a layer of perlite, and a little soil, then pulled out all the tiny plants I'd picked out. This is the moment I realized that the mini orchid was still way to big, I returned it. I added soil and figured out the plant arrangement.
Once the plants are arranged give it a good watering, this will also help clean the dirt from the sides and leaves. I let mine sit for a day then popped the cork in. Ideally these plants will thrive and the only time I'll need to open the jar would be to prune if things get too big.
I love terrariums for the rare occasions when I can cheat and open the lid, the smell inside takes me strait to a lush rain-forest. Since this was a thrifted jar and tiny plants the whole project cost less than $15.