I second the griffiths gnat for dries. I tie mine mainly in sizes 20-22 and catch more fish every year on them than any other dry.
95% of my flies can be tied in around 10 min or less. I don't get complicated and still catch many fish every year.
All good advise above.
Hares ears, pt, walts worm, SJW, Green weenie, eggs, etc. Tie a ton in different colors and sizes and you should be fine.
My streamers consist of woolly buggers in different sizes, colors and weights, clousers, and an all white marabou. That's about it with a few random things here and there.