What should I use while fly fishing in upstate new york?

I recently started fly fishing and I am heading out with a couple friends to a river. I don't know what type of fly I should use because alone I have had no luck. My father fishing with a spincaster and is catching browns, walleye, a northern, and weve seen trout. I don't care which Icatch I just want to know what flys I should use/ what line!