The ancient Greco-Roman gods have been around for millennia. They have often taken different shapes and different names, but they are a good starting point for many people. Part of the advantage of the Greco-Roman Pantheon is that each was created as an aspect of a heavenly body (Venus, Mars, Etc.). For obvious reasons, these are also used extensively with Astrology (which I know very little about... But I know someone who knows tons if you are curious about Astrology).
People often even create their own gods to reflect different aspects of their life. There is nothing wrong with this at all. A god is used to represent a specific part of the Universe, so that we can better work with a piece, instead of the whole. Some gods are considered very common, and are used especially when a group of people are Together, and they want to collaborate on the same concepts effectively.
There are literally hundreds of commonly used gods. It would be very difficult to have all of their attributes memorized at all times. There are a lot of research materials on the web, and in books that will give you a good set of gods to start learning about.
Bright Blessings
Downloadable books (free):
Sir William Stirling Maxwell - The CanonAleister Crowley - The Necronomicon
Solomonic Grimoires - The Greater Key Of Solomon Part 2
