Are you looking to purposefully leave whole or overlap on domains/portfolios for the gods?
I think you may want some patron gods to help fill out the ranks, 20-40 gods is a lot without crossing religions. Egyptian, Greek, and Norse have a lot of interesting gods. Mine them, then add patrons for certain cities and locations. A god of waves, a god of city X, a god of a haunted grove. If you play Magic, or even if you don't check out the
Kami each are gods (or spirits considered god-like) in their own right, and there are a lot of them. A god of the hearth? Moss, lanterns, pain, etc. Each has a god. That could help give you ideas to fill out your god quota.
This is a better listing of the kami, including those who don't have kami in the name.