Giant African Millipede enclosures and substrate?

I keep seeing conflicting info, so can someone either tell me what to use or post a picture of what they have? I was thinking a 40 gallon tank, but I’ve seen plastic bins used which would be nice since it’s a lot cheaper. I’m still not sure on what substrate to buy, and what to keep humidity/temps at.

I want this all setup and ready to go before buying the millipede. For reference sake I’m used to bioactive terrariums already with my dart frogs.