Help with substrate mix - short-grass prairie

[Bakuphoon]

I'm having trouble finding a substrate mix to use for my western hognose snake's vivarium. Most guides I've found are for tropical mixes, and that's understandable 'cause tropical plants are more colorful or somethin' :V

I'm trying to create some sort of short-grass prairie environment to emulate the natural habitat of the western hognose. The plants I plan to use are blue grama and buffalo grass. I might have one kind of flowering plant if I have the room. From what info I've been able to gather the substrate needs to be dry and easily drained, but I don't know what materials to start with.

I have a bit of experience with planted aquariums but this will be my first venture into vivaria. Any help is appreciated!