Can some one teach me about Celtic religion?

k since I wanna become a druid I gotta know the names of all the celtic gods and goddesses and Celtic stories. But obvioulsy you cant teach me all of them so i just need to know the names of the gods and what their the god of and HOW celtic religion began in Ireland- for example: christianity started because Jesus taught it to everyone in Roman times. And one more thing do people still practice Celtic mythology? its so sad how Celtic is becoming extinct... Any sites were i can learn to practice celtic? And what is the celtic symbol for the religion for example-for christains its a cross and for jews its a star.