On group rides with more than one other co-rider: One tube only, regardless of ride length. You will get help when needed.

On solo rides (or one other rider only):
<50 miles: One tube + patch kit
50+ miles: Two tubes + patch kit
You could do the 50 miler with one tube+patch as well, but I like to have backup in the rare case that the tube is unpatchable, like a valve type puncture that can't be easily patched.

I love patching, but I've never had to patch on the road. But I've patched often enough at home that it would definitely be a trivial task. It's super-uber easy - just don't use the 'preglued' patches, as those fail much more than the separate glue ones, which for me, have never failed - not once. Even my rookie patches worked great.

Once you do a patch and see it holds, you'll never be afraid of on-road flats that strand you ever again.