Selecting your plants is the first step to any type of terrarium or potted garden. Depending on the light level of your space, plant options will vary. Don't assume that all succulents need direct sunlight. There are a variety of low light succulents that will thrive with indirect light. Learn to identify many common succulents with this list from BHG, and before heading out to purchase your plants check out this post: How to Shop for Plants: A Black Thumb's Guide.
The succulent medley in image 1 is a composition I put together of low light plants. There are 7 different succulents in this pot, varying from 2" diameter to 6" diameter plants. The pot sits near a north facing window in my apartment and requires minimal watering, roughly once a week. I packed the container with cactus soil, the prefered medium for growing succulents. After planting the succulents I topped it with lava rock to hide the dirt and give it a cleaner look.
Hanging terrariums and aeriums have been trending for awhile now. While the simple glass bulbs we so often see can be quite beautiful, there are a variety of options for hanging containers if you're searching for something outside the norm. The geometric hanging terrarium in image 2, from Score & Solder, mimics the shape of the plants it contains. Check out Wit and Whistle for the tutorial.
As with any design project, composition is important. Think about color, scale and shape when selecting and placing your plants. Combine a tall plant with a few that that grow horizontally and/or consider using similar shapes in a variety of sizes. Don't be afraid to add something of contrast for a point of interest. Mixing and matching is the fun part — just be sure to pair plants that require similar amount of light.
If budget is a concern, there are options for composing terrariums of found materials or sprouting new plants from existing ones. The glass tabletop terrarium in image 3, from Madey Edlin, combines sand, collected beach rocks and soil for its base. Whether you're building a terrarium or aerium, consider found mosses, branches, collected shells, and rocks. Learn how to propagate succulents here.
Indoor succulent containers do not require a drainage hole, because they should never be watered to the point that water leaks from the base. These plants prefer to dry out between each watering. If the soil stays wet the roots will rot, so be careful not to overwater.
Tillandsias or air plants (image 4) are even more low maintenance than potted succulents. Follow these directions from Houzz to create the lovely composition and container in image 4 with a single plant and no soil.
(Images: as credited above.)