Hi @Peewee,
Welcome to the Bunnings Workshop community, it is wonderful to have you with us.
I think it all depends on what you are planning to use your terrarium for.
If it were to house reptiles, it would be a bit more specialised, so I would suggest speaking with a pet store or reptile specialist for their assistance.
If it were a plant housing terrarium, then you can check out How To Make A Terrarium and How to make your own terrarium by @mich1972 for some guidance.
You're going to need a glass terrarium container. There are quite a few options for terrariums, so have a look and see what you like.
You'll then need horticultural charcoal as a base layer, Pebbles or Propagation Sand, and a potting mix suitable for your plants, such as African Violet Potting Mix or Cacti & Succulents Potting Mix.
You'll want to add plants such as cacti or succulents, ferns, moss or sedums. Basically, anything small that will thrive in a humid environment.
Don't overcrowd it with plants, and consider adding decorative items such as branches, decorative stones or small garden ornaments.
Make sure that you only ever water with a spray bottle as terrariums do not require a huge amount of water.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
