You can use an adjustable wrench as a gauge.
Snug up on a thinner spoke and then see if it slides over a thicker spoke.

I currently have 1 thicker spoke on a wheel I built because of a head failure.
I'll buy a replacement when i make my next spoke order, but I'm not going to worry about it in the mean time.
I'm sure it has a different pitch when plucked, but I don't care.

You really need to focus on the BASICS!