People can answer this in the vivarium forum, but for soil, if you want plants you can make a mix of things. Sadly dirt from a garden/ forest is likely to have insect eggs, parasites and stuff in it. Most potting soil has chemical fertilizers and shouldn't be used.

You can use rocks for drainage, it'll just make the terrarium heavier and harder to move. There's some light clay-based drainage stuff you can find in garden stores that works. But clean rocks will work too.