Gender classes, which to use?

I am thinking of making a simple gender-class system
somewhat like Bantu languages. The idea might be to
use the initial consonant to indicate class, e.g.

B... = animal   F... = tool             J... = groups
C... = plant    G... = artifact         K... = substances
D... = human    H... = other object     L... = foods

So if I had 20 or so categories what might they be,
how best to categorize all of creation?

This might work nicely as a sort of hash table,
but then it might be very tempting to use the
initial vowel as well ...