Varivas 2300 Ultra Midge Hooks, Size 20
The Varivas 2300 Ultra Midge hooks are the smallest I carry. Currently, I have them in sizes 20, 28 and 30. They are well suited to tying extremely small soft hackles or Stewart Black Spiders using the small feathers found on a starling neck. I would suggest Veevus 16/0 thread. The hackle and thread are all you need. There are many, many midge patterns that you can find online, but I have not found micros to be very selective.
I use the size 20 as my "go to" hook for keiryu fishing with a red wiggler. Red wigglers are small worms, small enough that some people claim they are too small and you can't hook them. Nonsense! Most of the things a trout eats are smaller than red wigglers, and the small size of the worm insures that if a trout takes your worm, it gets the hook, too.
Hook a red wiggler once, crosswise, in the middle of the worm. If you use a gentle cast the worm won't come off. You won't have to "set the hook." Just tighten the line and the fish will be hooked.