Basics for a sorority:
TONS of plants (silicone, fabric, silk, live) that are low, medium and tall plants, along with perhaps some floating.
For a 30, you could do with bettas for the top level, a type of fish for the middle level, and bottom feeders such as cories, or even shrimp (with hiding spots!!)
- Head and Tailight Tetra
- Rummy Nose Tetra
Do note all fish tend to wander to the surface or the bottom for scavenging/food or other reasons, so no one will stay in their "level" of the tank... I would avoid long finned, super colorful, or aggressive/nippy fish. Female bettas can be worse than male bettas, and they can gang up on other fish, so keep the colors softer, pastel-like, and fins short!
Breed for the breed, not for the money; the words any REAL breeder would understand.
You must know nothing in order to know all, for all is nothing and nothing is for all.