Gold is not a very good conductor at all. RCAs and tube pins, etc are plated very thinly(as you observed) simply because gold does not oxidize. Silver's conductivity is not affected when it tarnishes, but it looks bad, so most people that sell silver connectors on their interconnects(like Silver Audio) include a special cleaning cloth with them, Actually the best connectors are made of solid, oxygen free copper. You just have to make and break your connections every so often the keep the juice flowing properly. Caig Deoxit is great for cleaning connectors, and blocking oxygen/dirt from the contact area.
DIY solid gold interconnects?
I have an 8wpc amp using el34's connecting to a McIntosh MX130 pre-amp to an Esoteric Z500, Plus some other stuff for HT. I recently read an article about the use of single wire connects. It seems to me that the best connects would be made purely of a single 12-13g rhodium plated solid gold wire that would be encased in something else. What I do for a living would make this quite possible and easy for me to concoct, but I would like some input as to weather or not this would be the way to go.