What I want to create is a simple logic gate that doesn't actually perform any logic, but instead simply repeats the given signal. I want to do this so that I can have a one-way wire.
Some ideas that I've thought of, but I'm not sure if they're efficient, or which one is more efficient:
A NOT gate plugged into a NOT gate.
An AND gate with both of the inputs as the same wire
An OR gate with both of the inputs as the same wire.
What you're looking for is commonly known as a "buffer". Any of your proposed constructions would work to form one; I believe the two-cascaded-NOT-gates is common in CMOS logic.
Buffers are another option, but really "one way" is the default of logic signals. You do have exceptions where tri-state gate outputs are connected together, wired "OR" and perhaps some other exceptions.
The buffer or non-inverting gate construct will delay the signal by a bit and might provide stronger drive, which are useful in some circumstances. Sometimes you want true and complementary outputs that change at almost the same time, such as this one.