For fishing the local streams to small, nonselective trout, I go light and generally only carry two small boxes. A foam Morrell that is 3 inches by 4 inches and a aluminum Okuma that is 2.5 by 3.5 with 6 individual closing sections for dry flies. I carry a mix of flies in the boxes that have covered all the "hatches" I have found locally--mainly ant patterns and small stimulators.
Here's the Morrell:
Outside:
Here's the Okuma:
Outside:
The nice thing about the Morrell is it weighs practically nothing and if dropped in the stream floats like a cork--you just have to be fast enough to catch up with it as it charges downstream.
The Okuma holds a lot of small dries. I carry adams, ants, some small humpies, royal wulffs, and some stimulators. These boxes take a beating. Note the big dent in mine. Doesn't affect functionality at all.
Now for destinations where I need wider variety, I keep boxes broken into fly types. I have morrells filled with nothing but caddis, ones filled with nothing but baetis, streamer boxes, nymph boxes, etc. I keep many, many flies in boxes in my car when traveling, and create boxes at location to mimic what I find on the water any given day. For example, the Lower O in February--better have lots of baetis/BWO/zebra midge; March/April--lots of caddis. Streamers are also good to carry on that river all the time.
Have fun organizing the flies. I'd say 5000-10000 ought to do it.
"Should you cast your fly into a branch overhead or into a bush behind you, or miss a fish striking, or lose him,or slip into a hole up to your armpits-keep your temper; above all things don't swear, for he that swears will catch no fish."