Making a terrarium is easy and cheaper than you think. Each plant 2.95 at a home improvement store, rocks 1.00 at a dollar store and glass easy to find at a thrift store.
Online instructions say you need cactus soil, but cactus soil is just like potting soil with extra sand. I had potting soil, and play sand, so I mixed to too to get a good consistency. Succulents need lots of drainage so add rocks to the bottom of your glass. I found pebbles at a dollar store for a dollar a bag and I used 1.5 bags. One bag for the bottom, and less than that for the top to give it a finished look.
I ended up making two. The second one cost me a grand total of $13. $2.00 for the rectangular vase from a thrift store, $9.00 worth of plants, and $2.00 of rocks. I had the sand and potting soil already.