The main dry flies I use I can count on one hand. It does not have to be a mystery, and I think this is why there is a growing attraction of Lake Fishing and indeed of the craze of stocking monster genetically altered trout species.
The Hawthorn Fly: These little flies are represented well by a black hackle with peacock herl body and legs. An all rounder for all hoppers.
Iron Blue: The dun is particularly good and I think represents a variety of critters.
Light and Dark Olives: These are about all year ether one or the other.
Black Gnat: This is small and black what more can I say!
The above is quite a short list but they work all the time. During the year a specific hatch can make the fish fussy. So you will find its useful to keep maybe two of the below in your emergency compartment of your fly box.
? The Light Green May Fly.
? Crane Flies ( daddy long legs ).
? Blue & Red Damsels.
? Blue Bottle.
? Flying Ant.